Code P0305 cylinder 5 misfire on LSS

Ok, this may be a lengthy post but I'm giving as much info as possible. I have a cyl 5 misfire on a 1996 LSS. This only occurs at high RPM. I did a freeze frame and here is what the reader returned:
RPM: 4413
Load value: 67%
Airflow rate: 116.85 GR/Sec
MAP sensor: 95KPA
Coolant temp: 158F
Short term fuel trim 3: -96.7% (this is VERY rich)
Long term fuel trim: -18.8% (rich)
Speed: 36MPH
Fuel system 1: open
Fuel system 2: N/A
I have replaced the following:
Coils
Ignition module
Spark plug wires
Spark plug
Fuel injector (#5)
O2 sensor
MAP sensor (I damaged it while checking). I haven't done a compression test yet, so this could point to valves, etc. No other codes appear when I have this failure. The car passed emissions last month (yeah, they just hook up the OBDII reader to it) but is there anything else I'm missing? PCM reprogramming? When you run the car under normal acceleration, the code does not appear. If I "punch it", The SES lamp flashes and the Traction Off lamp turns on. So if anyone has some more checks or ideas, post away!

How long was the engine running here, the coolant temp is low and you are in open loop( full throttle run?) Did the plug on #5 look any different than the others? How is fuel pressure, look for fuel in the vacuum hose to the regulator also. The rich readings are a result of the misfire, can you feel this when it happens?

Sorry that I haven't replied, I work nights at a really BIG semiconductor company and we have OT available (I need it to fix this problem!). The old plug had a black sooty deposit on it. The cool temp is because I had just started the car up and it was not fully warmed up. I have checked the compression on cyl #5, it was OK. I replaced the fuel pressure regulator, no help. There was no fuel in the vacuum line. I also found a fuel leak at the supply quick disconnect. I replaced the quick disconnect and the O-rings, fixed. I did a fuel pressure test after all this, pressure with ignition on was 35 psi (spec says 40 to 47). Fuel pressure with engine on and at idle is 40psi. I can't feel the misfire when accelerating but I can when the car is sitting in park (I feel the misfire at around 4000 RPM).

There is another problem that may or may not be related. The cruise control accelerates slowly when it is engaged (won't hold speed). Turning the cruise switch off or tapping the brake doesn't shut it off. The only way I have found to disengage the cruise is to put the transmission in neutral and tap the accelerator. When I do this, the RPM jumps to 4 grand and I get the misfire code and sometimes an idle air control code. Looking at the fault tree for cruise control the manual says to replace the PCM. Could a faulty PCM be the root cause for both problems?

The pcm rarely is an issue with a misfire, remember at 4k in neutral the pcm cuts the fuel to save the engine.