Hey guys, not a K5 question, but still a Chevy. This one has me stumped. Here it goes. My wife's '91 Caprice Classic is having issues. The car has a 5.0 (305), 700R-4, 3.42 posi rear, and the normal 2bbl TBI setup you'd find on some Camaros, and all '87-'95 trucks. The original motor, trans, and rear end all have just under 300,000 miles on them. Until now you'd have never known or guessed it had that many miles on it because it still runs great. Up until this problem, I have only changed the water pump, Alt, knock sensor, fan clutch and fuel pump. It all started in November of '03. My wife came to me and says that the car likes to fall on its face ramdomly when taking off from a light. I check for codes first and nothing is stored. So I change the fuel filter, run a few bottles of "fuel injector cleaner" through it and nothing changes and it still does it on occasion just like before. So, some time passes and nothing really gets worse and to be honest I didn't have the money to mess with it anyway. Then last week she wakes me up one morning and says it won't start. She also tells me its been giving her "check engine" lights on her way home for the last few days and forgot to mention it to me (women!). Again, I check for codes with my scanner and to my suprise....nothing is stored. That in itself is odd to me why she would she a light, but the ECM didn't store it. Anyway, I crank the motor for a good 30 seconds and it finally starts and idles very smooth once running. I rev the motor alittle while still in PARK and the motor stumbles, everytime I rev. Doesn't matter if I do it slow or fast, it stumbles just off idle. I took it for a drive and had it die on me when leaving a stop(s) if I gave it more than the tinyest amount of peddle to get moving. I was able to get to 65 mph, once it got to speed it drove fine. I get it home and do a complete tune up. I changed the cap, rotor, wires, plugs, change the oil, air filter, another fuel filter, and thermostat. No change. Then I changed the ignition coil (external), MAP sensor, tested the ignition module, checked the timing, and checked the fuel pressure after the fuel fiter (near the pump) and at the TB, both inline, both read 12 psi. The book says it needs to be between 9 and 13 psi. That means its its not the pump or the fuel pressure regulator, right? Still no codes either. At this point I am totally stumped. If any of you have any ideas, please tell me. If you need more info that I didn't mention, just let me know. Thanks guys.