1990 5.7 TBI dies under load

I have a 5.7 TBI that will start up and idle ok but as soon as you give it gas it tries to die, weather it is in park or in gear. The problem seemed to get gradually worse over the last year until recently the problem made the truck undrivable. I have replaced the fuel filter, rebuilt the TBI unit, changed the map sensor and none of these things worked. I can't figure it out???? Any ideas would be great.

Have you checked the fuel pressure? Your fuel pump may be going south..

A bad converter or blocked exhaust can also give this symptom. Might want to check the exhaust backpressure to see what it is at.

90 Factory Manual says: at idle with engine warm, pressure should not exceed 1.25 PSI. At 2000 RPM, pressure should not exceed 3 PSI.

//2000CAYukon