95 Monte 3.1 V6 floods, drives me nuts

Ok, I'm officially frustrated. I"m out of ideas how to get this fixed. Here's the problem:
Engine was replaced with a GM crate engine. So any mechanical failure from that area can be ruled out. Engine starts, runs for a short while then stalls, plenty of black smoke coming from the exhaust, raw fuel is found in the intake and EGR.
IAC, TPS, Fuel Filter replaced. Same thing. EGR, cleaned, one valve was stuck, same thing. Floods and stalls. Fuel pressure regulator, tested diapraghm, holds the vacuum, no fluid leaking from that side. Applied pressure to the regulator through air compressor, regulator opens. Disconnected battery to reset PCM, same thing runs for a while, floods, stalls. Checked all spark plug wires for proper resistance, they check out, Spark plugs, new. 95 has no MAF, so that one can be ruled out. Don't have a code scanner handy, on my Buick i can jump terminals to get the codes displayed on the dash, doesn't work on 95 Montes, only has two wires in the ALDL connector. Fuel injectors under pressure won't drip.
I have checked the internet, and a lot of folks seemed to have had that problem , but nobody really posted the fix.
Anybody with an idea out there what could cause this?

Do you have full manifold vacuum to the MAP sensor? Preferably a single line from the MAP sensor T-ed to nothing else or just the Fuel Pressure Regulator.

16 pin OBD1 ALDL connectors don't have the shorting pins to reveal the codes. Some 94/95s use the 16 pin connector. You can however use TunerPro RT and the ALDL to USB cable I sell at http://reddevilriver.com to both read the codes and read all the sensors.

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a 95 monte w/3.1 has a 12 pin connector.... or at least mine does.

when you say a short while, about how long are you talking? 30 seconds?

Runs for about a minute. Then it starts to smoke. Regarding the map, it is hooked to full manifold vacuum. When the car runs and i take off the vacuum line from the fuel pressure regulator I get a hissing sound, so vacuum shouldn't be the problem.

Unplug the O2 sensor and see what happens.

This is where a scanner would be real helpful. You could see if the ECM is reacting to a bad input that is telling it to dump fuel in or not. Is this problem happening when the ECM goes into closed loop? When the engine is running way rich is the instead the ECM seeing it as rich? (indicating a non-ECM fuel problem) It's hard to tell these kind of things without a scanner.

yeah. I know a scanner would be helpful. I was hoping that while I'm waiting to get one, someone would come up with a genius solution ;)...
O2 looks like it was replaced a short while a go, but I know that doesn't mean a thing. Will try and start the car with O2 unhooked and see what happens.
I do have a GM service Manual for the car, and the only other areas I haven't looked at are the Map, ECM and O2...

60 seconds is about right for closed loop at these ambient temps, i'd do the O2 disconnect. the BLM/INT limits in the P66 V6 calibrations are crazy(BLM: 100/156 INT:16/240), so i can see it getting sent rich or lean enough to cause a stall easily.

Changed the ICM, Map, same darn thing. Floods and stalls.

...and unplugging the O2 gave the same result, floods and stalls