stealth rt problem please help!!

I have a 92 stealth rt 3.0 dohc. I had a problem with a leaky gas tank... well it turned out it was a leaky pressure hose but I had the gas tank and fuel filter changed and the pressure hose changed and after I got my car back I started having a weird problem. Under heavy acceleration my car would only accelerate to 4000 rpm and then the rpm's would drop to idle. 2 days later this would happen even at 2000 rpm. so i changed the ECU since the capacitators were melted already and the circuit board was burned and then i took the car for a test drive only to find that it has the same problem at around 3500-4000 rpm. It's weird... i'm thinking it could be the fuel pump... or maybe the oxygen sensor? The check engine light used to come on but since i replaced the ECU it's been off.

Anyone have any ideas of what's going on?

Only thing I can think of is maybe a blockage in the new fuel system. Like a pinched fuel line or something.