I have a 91 firebird 5.7L tpi. I just finished rebuilding the engine in my garage and got the engine in the car. It has trick flow heads 175cc 56cc chamber's. I know there small but they flow alot better then the stock ones it also has edelbrock high flow base and runners and 52mm throttle body 1.6rr headers and the cam is stock. I finally got around to starting it last weekend fired right up no session light. I timed it at 6 * btdc has good throttle response in park. The only thing that is bugging me is it will idle around 750 when I start it but it will surge between up to 850 and if I give it a little shot of gas it won't go back down to 750 it will surge between 9-1100. I tried really quick to test the tps but I couldn't get a reading off any ideas would be helpful

 

Surging is usually caused by a vacuum leak. Check all of your vacuum lines.