I cralled under my new GMC, LLY, 4x4,CC,sb tonight and found what looked like a cooler for fuel is this on all models or is it new to the LLy and does anybody know if it cools return fuel or supply fuel.

It's on all DMAX trucks. It cools the return fuel from the engine.

COOLS THE FUEL FROM THE ENGINE,DEALERS SAYS TO KEEP IT CLEAN TO EFFECIENTY COOL THE FUEL