Duramax LLY Downpipe Upgrade Guide
When the GM Duramax LLY was launched halfway through the 2004 model year, it represented a step forward in the Duramax diesel engine family. The LLY took the place of the outgoing LB7 Duramax and improved upon some of the LB7’s shortcomings. While the Duramax LLY was an unquestionable improvement over the LB7, it still…