Since 2001, five versions of the 6.6L Duramax diesel has been produced. These diesel truck engines are designated by year and 3-letter code. The Duramax engines are LB7, LLY, LBZ, LMM, & LML. When combined with EFI Live and ATPTrucks custom diesel tuning expertise, the 6.6L Duramax is a dominate force to be reckoned with. Don't hesitate to call us with any questions about diesel performance. Our experts are ready to help you attain your goals.