ts5089

I'm helping a buddy that has a 93 Lt1 350 in a 32 Chevy convertable. The motor has a very bad stumble when you hit the throttle. I have found several thing I thought was the problem, but it still stumbles. I checked the fuel pressure at the pump and had 45psi and it increases when the throttle is hit. I replaced the fuel rails because the feed side was kinked bad, then I found the motor had the wrong spark plugs, it had the washer style and needed to be the tapper seat style, then the computer said the thottle position sensor was bad, relaced it. Any help would be greatly appreciated.
Thanks,
MIKE