need help! on 1990 Chevrolet Celebrity

I am having trouble with my 88 celebrity 2.8l v6! A week ago was driving up hill and when reached 60 mph, it stalled out, and let out little black smoke. by the end of day it started to stall around 30 mph, or when i put load on the engine it would stall, now i cant get it to start. if i do it runs a couple of seconds then dies. I have replaced the fuel pump, pump relay, fuel filter, replaced ignition coils, computer, prom, and crank position sensor. there is pressure of 40-42 at start, I tested the ignition control module,20 time 8 from one store, 12 from other and passed every time with no hesitation. I have fuel, spark, and pressure, but will not run, I even went as far as to check wiring to make sure didn't have short out some where...everything's fine!I have no injector pulse but from all six to go out would be strange.... Please help!

2 answers
On these engines, shorted injectors are very common. The resistance should be around 12 ohms +/- 1 ohm. When the injectors short, the ecm goes into ckt protection and will cause a stall condition. Many times the shorted injectors will damage the ecm. You can only get to two of the injectors to check the resistance without removing the upper intake manifold. Good luck. A rebuilt set of injectors runs about $100.00. Let me know, we have a set on the shelf ready to install.
I suspect there is an exhaust restriction. Possibly a clogged catalytic converter. Have this checked.