2004.5- 2005 GM 6.6L LLY Duramax | Engine Tuning by PPEIElevate your 2004. 5 2005 LLY Duramax to new limits with PPEI's Engine Calibration, an industry leading performance enhancement that will transform your truck's capabilities. PPEI's Engine Calibrations have been meticulously crafted to unleash the full potential of your LLY Duramax, providing a significant performance boost of up to an additional 230 HP directly to the wheels. But the advantages of PPEI's tuning go far beyond raw horsepower. These