DIESEL
PERFORMANCE
FAQ

The correct sequence is fuel system first, then tune, then supporting components (intake, intercooler, exhaust), then turbo upgrades, then injectors. The fuel system always leads — not because it adds the most power, but because it protects everything that comes after it. A performance tune increases fuel demand at the injection pump inlet. Adding that demand without first protecting the pump with a lift pump and clean fuel supply is how CP4 failures happen. On CP4-equipped trucks, the lift pump and, where applicable, the CP3 conversion are prerequisites — not optional additions. After the fuel system is secured, the tune is calibrated around the available airflow. Then supporting mods extend the range of what the tune can do. See our build process page and fuel system upgrades for the full sequence.

Build time depends entirely on scope. A Stage 1 tune — lift pump, EFI Live or HP Tuners calibration — typically takes 1–2 days. A Stage 2 build adding intake, intercooler, exhaust, and TCM recalibration runs 3–7 days depending on parts availability. A Stage 3 compound turbo build with injectors and transmission work runs 3–5 weeks. Competition builds — sled pull or drag prep — add time for trans brake installation, dyno time, and road or track validation. Every build starts with a consultation to scope the work and establish a realistic timeline before anything comes apart. We don't start a build we can't complete correctly within the agreed timeframe.

At Stage 1 and Stage 2, the factory transmissions on all three major platforms — 68RFE, Allison 1000, 6R140 — do not require a full rebuild. They do require a transmission calibration recalibration to match the increased torque output. Running a Stage 2 engine tune without adjusting the transmission calibration produces harsh shifts and accelerated clutch wear. The TCM calibration is part of the tune package, not an optional add-on. At Stage 3 power — 600+ rwhp, aggressive compound builds — a full transmission rebuild becomes part of the build sheet. The transmission upgrades page covers this in detail by platform.

Platform determines the tool — not shop preference. EFI Live has full ECM and TCM access on Cummins (all model years) and Duramax through LML (2011–2016). HP Tuners has full access on Duramax L5P (2017+), Ford 6.7 Power Stroke (all model years), and F-150 3.0L Power Stroke. For Cummins trucks, EFI Live is the calibration platform regardless of what year or generation — there is no HP Tuners alternative for Cummins. For 2017+ Duramax L5P, HP Tuners is the platform. For all 6.7 Power Stroke trucks, HP Tuners is the platform. We use both — the truck's ECM architecture determines which one we use. See the engine tuning page for the full platform breakdown.

The DSP5 switch is a 5-position rotary dial mounted in the cab that allows switching between up to five stored EFI Live calibration profiles without a laptop. Most trucks we tune get at least two profiles: a street/daily tune and a tow tune. Trucks with both street and competition use get three profiles (street, tow, pull or drag). The switch costs under $150 and is standard equipment on every EFI Live build we do — it turns a single tune investment into a versatile, use-case-optimized system. HP Tuners uses a different multi-profile switching method via the phone app on some platforms.

The CP3 (Common Rail Pump 3) is a gear-driven, three-piston radial pump. It relies on fuel for lubrication but tolerates aeration and inlet pressure variation reasonably well. The CP4 (Common Rail Pump 4) is a cam-driven, single or dual-piston pump that is significantly more sensitive to inlet conditions. CP4 failure — caused by aeration, water contamination, or insufficient inlet pressure — is catastrophic: the cam lobe destroys itself and sends metal debris through the entire high-pressure fuel system in milliseconds. The repair cost is $10,000–$18,000 or total loss. CP4 pumps appear on 2019+ Cummins 6.7, 2011+ Duramax LML/L5P, and 2011+ Power Stroke 6.7. On 2019+ Cummins and Power Stroke trucks going into performance builds, we do a CP3 conversion before any tune. See fuel system upgrades for detail.

On CP4-equipped trucks at any power level, a lift pump is a strong recommendation. CP4 failure is driven by aeration and inlet pressure variation — conditions that exist at stock power. The lift pump is CP4 insurance, not a performance upgrade. On CP3 trucks at stock power, a lift pump is less urgent but still beneficial — the CP3 is more tolerant, but consistent clean fuel supply is always better for injection system longevity. Our standard is FASS Titanium Series frame-mounted; the specific model is sized to the build's fuel demand. See the FASS page for model selection by platform and stage.

Yes. A CP3 conversion on a 2019+ Cummins or Power Stroke can be reversed — the factory CP4 can be reinstalled if a future owner requires it. The conversion itself is not destructive to the block or engine. However, in practice, most owners who have had the CP3 conversion done and understand the reason for it prefer to leave it in place. The CP3 conversion is not an emissions-affecting modification — it does not touch the DPF, SCR, DEF system, or EGR. It is a reliability modification to the high-pressure injection pump. That said, we keep the factory CP4 if the owner wants it retained for documentation.

For street performance and towing, all three major platforms — Cummins 6.7, Power Stroke 6.7, and Duramax LBZ/LML/L5P — are capable of strong Stage 2 and Stage 3 builds. The correct answer depends on the use case. For compound turbo and sled pull builds, Cummins has the deepest aftermarket and most established compound platform. For towing-focused builds, Power Stroke trucks have a strong towing calibration baseline and the 6R140 is a solid platform. For Allison transmission buyers, Duramax is the natural fit. For competition, Cummins is the most common choice — but all three platforms have competitive presence. We work with all three platforms at every level.

The 2019+ Ram 2500 switched from a CP3 to a CP4.2 injection pump — that is the primary difference that affects the build path. On 2013–2018 Cummins trucks, the CP3 is already in place and the fuel system conversation starts with lift pump sizing. On 2019+ trucks, the CP3 conversion is the first line on the build sheet before any tune discussion. The engine itself (6.7 Cummins B-series) is mechanically similar across model years. Transmission platform matters too: 2019+ trucks may come with either 68RFE or Aisin AS69RC — the Aisin is the stronger platform for high-output builds. See the Ram 2500/3500 Cummins page for the full model year breakdown.

No. Drop Forged Diesel builds emissions-legal trucks only. We do not delete DPF, SCR, DEF, or EGR systems. This is a conviction, not a limitation — a properly tuned diesel with emissions equipment retained outperforms most deleted trucks in real-world use while remaining street-legal and insurable. We will not tune a truck with deleted emissions equipment, and we will not install deletion hardware. See our emissions policy page for the full position and the technical rationale behind it.

No. The CP3 conversion replaces the high-pressure injection pump — it does not touch the DPF, SCR, DEF, EGR, or any emissions-control component. The emissions control systems on a converted truck remain fully functional. The CP3 is an injection pump substitution for reliability reasons. Texas emissions inspection does not test injection pump type — it tests OBD readiness monitors and visual inspection of emissions components. A CP3-converted truck with all emissions equipment intact passes inspection the same way a stock truck does.

A sled pull build requires six systems planned together — not just more power. The lift pump (FASS 150+), CP3 conversion (2019+ trucks), compound turbo configuration, trans brake valve body, full transmission build, and EFI Live competition tune all need to be specified as a coordinated system. A street Stage 3 build addresses most of this but does not include a trans brake or a dedicated pull calibration profile. The competition tune profile is separate from the street and tow profiles — the pull profile fuels past street safety limits and is not suitable for road use. EFI Live's DSP5 switch allows the driver to select street or pull profile at the staging lane. See the sled pull prep page for the full scope.

Yes — and this is one of the things we do well. EFI Live multi-profile calibration allows the same truck to run a street/tow profile and a competition pull profile from the same DSP5 switch. The street profile runs conservative EGT limits, emissions system function, and normal driveability. The pull profile removes those limits for the duration of a hook. The hardware — trans brake, compound turbo, FASS lift pump, upgraded injectors — is the same in both modes. The same truck can drive to the event, hook in, pull, unhook, and drive home. We have builds that tow goosenecks on Saturdays and pull competitively on Sundays on the same fuel and the same drivetrain.