Help me figure this out...

[mlambrecht82]

It sounds like you might be having a missfire. When you open up the throttle plate the extra air that the engine sucks in raises the compression in the cylinder, this makes it harder for the spark plug to spark. Check your plug gaps, and make sure that none of the plugs are fouled. It might have nothing to do with the plugs and it might be some bad plug wires. Or if you have a multimeter you could check your coils for the proper resistance. Put one lead on one tower for a coil and the other lead on the other tower for the coil. I can't remember off the top of my head but the secondary resistance should be somewhere around 15,000 ohms. If its lower than that it is shorted and will not produce enough voltage to jump the gap at higher engine loads. The fuel pressure sounds a little low, but that wouldn't cause the problem, that doesn't mean that it doesn't have anything to do with your fuel system, a partially clogged injector could cause a lean missfire at higher rpms. If you can get an injector balance test done. Or just by a $2 bottle of STP and see if that fixes it. I doubt that will, but it won't hurt anything. To me it sounds like something to do with the ignition. Have someone look under the hood while you rev the car and cause the problem, have them look and listen to see if the spark is going through the plug wires, or jumping across the boot. If the plugs are gapped correctly and the wires are good, and the coils are strong then that should rule out the ignition almost entirely. The PCM could have a screwey knock sensor that is telling it to retard the timing at that certain rpm where the engine has that certain vibration.
I hope this helps.