Ninz

Please help me out guys if anybody has had a similar issue or might have a suggestion. I just upgraded the entire fuel system and now have a flat spot at 4000 rpm. The only other mods performed at this time were long tubes and exhaust so I am thinking it is a fuel or PCM related problem. The OE tank was sumped and I removed the internal factory pump. I went with an Aeromotive pump, filter and adjustable regulator all plumbed with -10 to the pump and -8 to the regulator and rails then used the factory line for the return. Fuel pressure is set at 55 psi.
Once the engine gets to around 4000 rpm, it just falls on it's face. It almost feels like its on the rev limiter but if you baby it past the stumble, it will continue to rev to the redline without any problems. Stab it at any rpm below 4000 and it runs great up to that point. Fuel pressure remains constant and air/fuel is also good throughout the whole process (checked with a wideband).
When I removed the OE fuel pump, I just left the wires unconnected. Is this ok or could that be making the computer freak out? It almost seems ignition related but I can't think of anything I did that would effect this.

Anybody got any ideas??

Thanks