I have a 2008 Chevy Silverado 2500 hd 6.0with flowmaster dual exhaust.I purchased a GM Cold Air induction from the dealership and I love it. It increased my mpg 3-4.

 

I too have the GM CAI on my 03' Silverado plus theGM duel cat back exhaust. Although I didn't realize the MPG increase thatncharley gotI did realize an increase in power. That's probably the reason why my MPG didn't go up because I drive it a little harder now with a heavier foot. The best thing about the GM CAI is the way it looks. It's not made ofcheap plastic crap like most of the rest out there but it's well designed and makes you proud to raise the hood.It also uses a dry filter so it doesn't screw up the sensors like others do.Sure, it cost a little more but you get what you pay for and when the dealer does the install you also get 1 year or 12,000 mile warranty. Can the others say that, I don't think so.