I did find a bolt up it from STILLEN for the 3.7 engine and now it's no longer posted. Anybody know any other kits?

 

meh, after messing around with tuner cars for years I am not a big fan of aftermarket F.I. kits anymore; they make the car less reliable and getting the right tune is often dependent on a piggy back or re-flash which usually doesn't let you account for changes in elevation resulting in either too lean or too rich conditions. Then specifically for Hummers; if you use them for off-road bumping the engine around and occasionally introducing mud and water is only going to lead to problems.

Reliability > Power

Just my thoughts on it, maybe I am just getting old

 

don't do it, get nitrous LOL