Sounds to me like maybe your brake booster needs rebuilt or replaced, that could cause your piston problem. Look in your specter catalog, it tells you how to see if its bad. A weber would be a good upgrade, but put a header on if your gonna use the weber, those two in combo, will give you probaly 15-20% extra ponies. I'd stay away from the holley's, I haven't heard to much good about them.