honestly ted, your combo doesnt sound too crazy, the fast xfi is a KILLER setup and will control anything from a simple motor up to 6 second cars.
if you go on FAST's website theres a step by step buying guide and let me tell you their support is KILLER I have had to call them on a few occasions and for the extra money you spend its totally worth it. I had TBI originally in my car then went to carb and had a bastard time, after having an edelbrock efi (which worked great, just didnt support my boosted application since i had the older proflo efi), then getting my FAST setup, id NEVER go back.
honeslty its your car/money/decision but if it were me the season is coming near an end, why dont you stash cash over winter and buy the fast setup or a whole new harness (for the price of a new GM harness i am sure the fast unit wouldnt be much more, and its totally not hard to hook up.
if you have any questions about the FASt setup etc jsut shoot me an email
camaroracer1992@yahoo.com and ill help you as much as i can and/or i can refer you to my tuner.