Wehrli 01-04 Duramax LB7 4in Intake Kit with Air Box Stage 2 - WCFab GreyWCFab 2001 2004 GM LB7 6. 6L Duramax Stage 2 Intake Kit with Air Box. This high flow, fabricated aluminum intake pipe and air box enclosure with dry filter assembly replaces the restrictive plastic factory parts on your diesel for improved engine performance. All new design significantly increases air flow to your turbo producing improved horsepower and torque, quicker throttle response, and cooler intake temperatures by drawing cold air through the