I found that when i replaced my sensor it ran worse than before. Turns out that those sensors are quite sensitive to the wire length and any difference in resistance. Which makes sense considering thats how the sensor operates anyway, so I probobly should have thought of that when I bought it. I replaced mine with the oem style and it worked quite a bit better. Not sure if that would actually cause the problem but two problems could be arising. One is that as the engine bay heats up the wire for the o2 sensor (if its cheaply made) could change resistance, though it shouldn't and that idea is a bit of a stretch i think. Also the ecu only takes readings from the o2 sensor after it is up to temp, since the sensor doesn't function cold. I'm not sure what the time delay/activation temp is. Quick test though would be to simply disconnect the sensor and see if anything changes. May have to reset the ecu after you reconnect it though.

I finally got a fuel pressure guage mounted, ended up putting it on the fuel filter. At idle the fuel pressure stays at 40 psi, when you rev it up it jumps to 42 psi then drops and stays at 38 psi. Also, tested it at load with parking brake on and pushing the brake, I gave it gas and a bit of clutch to simulate driving while problem was occuring. While bogging down the psi went down to 32psi.
Does any of this sound like a fuel pressure problem?
Im wondering if maybe the lean condition is caused by larger then stock exhaust, no cat and one side of exhaust off cobra, And AFM from supra and intake airbox from cobra.
Im kinda of running out of ideas on this thing.

The FSM lists the fuel pressures that are in the proper range. On the filter, you'll not be getting the pressure at the injectors, so no idea what you should be seeing there. Pressure is supposed to rise and fall with engine load.

Tomorrow Im rounding up the parts to mount the fuel guage on the cold start injector. The reading at the filter should give me a baseline to compare the cold start mounting location, maybe if its different could implicate the fuel pressure regulator.

how is the gas tank? im assuming you change the fuel filter before all of this? have you checked grounds on the engine and to the injectors, i know there is a place in the harness where the injectors are all spliced together and a spot on the harness where the injectors ground to the intake manifold. it is a must that you have a good ground to the injectors. i wouldnt always assume heat as the problem either. i would check your coil grounds and the coil itself with an ohm meter against the fsm specs too. like 4 crawler said try the easy (free) stuff first.... if your im doubt of the fuel pump you might try pulling it out and inspecting the tank and the sock for dirt... a dirty tank would coause a fuel pressure issue for sure....

Might also want to check the fuel injector wiring and splices:

http://www.4x4wire.com/forums/showf...&o=&fpart=1&vc=1

If the splices are intermittent, the injectors don't open as they should, fuel flow is cut and engine runs lean.

I have checked for anything obvious. The ohms on the coil are within specs, and the fuel pressure is within range. I was unable to find the right fittings to adapt for cold start injector to mount pressure guage there. Its a lean condition that I need to solve. I think its why it runs so bad upon restart with partialy cooled motor. Its running lean while the fuel requirement are greater, do to partially cooled motor. Upon a complete cool it has coldstart injector to help out and it runs fine.

just making sure, check the injector wiring.. id bet that if your cold start injector is spraying fuel, your fuel pressure reg is fine... not saying its not your problem though. there is a second fuel filter that is a part of the banjo bolt on certain models (i think 85-87) that can clog too. a way to test the pressure beyond that point would definitly be a good thing to do. let us know.

Im starting to lean a bit toward the O2 sensor. Its got about 20k or so on it, and its a splice on Bosch brand. The problem started not to long after I installed the O2 sensor. Its just kind of a $133 shot in the dark.

Sparkplugs.com my friend. My NippenDenso (long snout, OEM) ran $45 bucks from there. FYI, check out your make/model price.