Hi, Keith. Not much available for these motors. You definitely want to go with a CAI, or FWI and the Magnaflow catback. From what I've heard, if you decide to put a different cam in, you will also have to change the lifters which will dissable your active fuel management.

As much as I love these forums, it would appear that the best information regarding performance mods for the GXP is going to be found in the LS4 section of LS1tech.com