downpipe
I added a downpipe and a Lew Tune to my GXP. Coupled with a CAI of my own construction it made a very noticeable difference.
That being said if i could do it over i would go headers right off the bat.
Heatwrapping the crossover is not going to offer any substantial benefits other than perhaps not heatsoaking the intake as much. A good transmission cooler will keep things in check despite the crossover being right on top of it.

