O/T: '92 Caravan missing

On initial startup, it's smooth as silk. After a couple minutes, it starts to miss a little, and gets progressively worse. Not just at idle, but at any RPM. It backfires through exhaust mostly, and some through the intake. There is some smell of unburnt gas, but I don't notice any black smoke.

New parts include fuel filter, crank sensor, cam sensor, temp sensor(by the gooseneck), oxygen sensor, timing chain, map sensor and spark plugs.

Coil pack, TPS, computer and IAC have been changed out with spares; made no difference. Originals are reinstalled now.

Fuel pressure is about 45 lbs. with the pressure regulator connected, about 53 lbs. with the regulator disconnected.

Muffler is new, and catalytic converter is not plugged(as in, he knocked everything out of it. It is simply a hollow chamber now). I'm assuming this was done as a diagnostic step, and he plans to install a different one after the problem is cured.

I'm 95% sure it was run empty, and has fresh gas in it. Yes it has sat for a couple months, but I don't think stale fuel is the problem.(I hope?)

The Check Engine light is not showing any codes in the computer.

The air filter is clean; no other obstructions to airflow.

I've posted here before about this beast and gotten some good information on things to check(wiring under the battery tray comes to mind). Electrically, I can't find anything wrong. Unfortunately, the cause of the problem still eludes me. Once you get it past the '10 minute problem' stage, it runs pretty darn good. A minor stutter here and there, but I'd say it's 98% of what it should be. As an indicator of how bad it runs, if you start it and hold the pedal so it turns approx. 2500 rpm, it will gradually drop to around 1000 rpm because it's so rough. Left at an idle, it will run a minute and stall. Usually you can hit the key and it will fire right back up, only to quit a minute later.

Opinions and suggestions are appreciated.

Thanks for your time,

Anthony

RT

Thanks,
Anthony