I currently have a 2003 5.3L Silverado and was at Advanced Auto Parts today and saw the Spectre CAI. It was reasonably priced and wanted to know if anyone has heard anything good or bad about this CAI. I also have a local mechanic/auto shop that offers a generic version of the Flowmaster 40 Series muffler. How loud is the 40 Series? Would the combination of the two give me an increase in MPGs if I am able to keep my foot off the pedal? Any advice or opinions are appreciated.