too much fuel pressure help!!

well the problem i am having with my 93z 383 is that when i start my car it is running way rich and just throws out raw fuel and i am fouling plugs left and right.
i did a fuel pressure check and at idle with vaccum line on i am about 40-45psi and with it off i am about 45-50psi and when i spike the throttle the gauge maxes out at 100psi then drops all the way to almost zero then sits back at its normal 45psi. also the gauge fluctuates back and forth 5-10 psi and makes it hard to get a good reading. car has a stock fpr with 42lb lucas injectors. car is equipped with a pcmforless tune set for the 36lb accels i used to have but i wouldnt think adding the 42lb'ers would give me the problem i am having now

im am leaning towards the fpr being the culprit any ideas would be greatly appreciated thanks.

You've increased the fuel injector flow constant by 16% without increasing the PCM programmed value. The PCM can only pull out 15% excess fuel with the long term fuel corrections. And the Lucas "disc" injectors are probably much faster than the Accel pintle type, meaning the offset tables need to be revised as well. You are inviting a severe rich condition in power enrichment mode (approx. "WOT"), since the PCM will be using the long term corrections to reduce fuel in closed loop, and when it goes into PE mode it will ignore the learned long terms and use "128". Its a huge waste to have an engine tuned for one set of injectors, and then just throw a set of much larger injectors on, without correcting the tune.

This does not explain the 100psi readings. Try "spiking" the throttle without the vacuum line connected, to see if it produces the same results. What type of fuel pressure gauge did you use? What fuel pressure do you see at WOT with the engine at max load/max RPM? Does the pressure ever exceed 50psi at any time other than when you "spike" the throttle - which I assume means you are rapidly opening and closing the throttle blades while the engine is idling and not under load?

well i replaced the fpr and now the fuel pressure is where it should be, and the car will actually stay running but its still running rich so i will send the chip out to get it reprogrammed for the 42lb'ers. thanks for the help!