he Southern Diesel Supply L5P Turn-Key Kit is a complete, ready-to-run tuning package built for Duramax owners who demand dependable power, sharper drivability, and configurable performance. This kit provides everything needed to unlock your truck’s full potential, combining advanced ECM tuning capability.

Featuring the MPVI4 interface and Southern Diesel Supply custom calibration files, this turn-key setup allows full control over engine tuning with optional Shift-On-The-Fly functionality. Whether your truck is a daily driver, tow rig, or performance build, this package delivers responsive power exactly when you need it—without repeated reflashing.

What’s Included

• Tuning Configuration Options
  Choose between a single performance tune or Shift-On-The-Fly (SOTF) tuning.
• MPVI4 Tuning Interface
  Industry-leading hardware for advanced Duramax ECM tuning and diagnostics.
• Six (6) Universal Credits
  Required for ECM unlocking and flashing.
• Coolant Upgrade Kit (MADE IN THE USA)
• Diagnostic Plug Kit (MADE IN THE USA)
• Material Choice

‼️IMPORTANT‼️

For ALL 2017 and Some 2018 trucks, the GM E41 ECM Upgrade Kit is still be required. Unfortunately, there's no VIN cutoff to determine which 2018 models need the unlock cable — you'll only know after connecting the MPVI3 to your truck and laptop and try and write your stock file back to the ECM. 

If you do need it, we offer the E41 Upgrade Cable for Rent (Click Here):
🔧 $100 rental fee
💵 $150 refundable core deposit

Once you return the cable, your $150 core deposit will be refunded.

We understand this isn’t ideal, but it’s the only way to confirm compatibility.

Note: This does not apply to 2019–2023 trucks.

Performance Levels

Southern Diesel Supply custom calibrations include size selectable power levels designed for everything from stock-like operation to aggressive performance.

• Level 0: Stock Output
• Level 1: +30 HP
• Level 2: +80 HP
• Level 3: +135 HP
• Level 4: +160 HP
• Level 5: +210 HP

With Shift-On-The-Fly enabled, power levels can be changed instantly using factory steering wheel controls, allowing on-demand adjustment without stopping or reflashing.

PLEASE TYPE YOUR VIN & TIRE SIZE IN THE ORDER NOTES. FAILURE TO DO SO WILL RESULT IN TUNE FILE DELAYS!