Engine Performance problem
1992 GMC Jimmy 6 cyl Four Wheel Drive Automatic 101145 miles
I have a 1992 jimmy 4x4 4.3l Vin w, I performed a tune up with cap, rotor and wire set as well as a fuel filter which was plugged, and sent the customer to the muffler shop to have the plugged catalytic converter replaced. The customer called and said the vehicle ran wonderful on her way back from the muffler shop. Then about 2 days later the vehicle was very hard to start after it was warm and sat for about 15-20 min. I rechecked the tune up and checked fuel pressure, found 45psi with key on and it would bleed down to 10psi within 1-2 min, spec is 55-64psi. I then proceeded to replace the pump and pulsator. After that I have 55-61psi and vehicle started great cold and the idled poor when hot. Someone has already replaced the IAC, EGR and CMFI unit under the intake. The coolant temp has also been replaced. I pulled the plugs for the hell of it and the drivers side plugs were fouled and the passenger side plugs were clean I am at my whits end, I can watch data with the scanner and the block learn will stay at 108 and the integrater will go down to 80. If I pull the map sensor out of the upper intake to create a vacuum leak the block learn and integrater rise and the engine runs better but the rpm does not go above 1045, Should't the rpm go through the roof with a direct vacuum leak like that? My gut is telling me that the drivers in the computer are bad, I am going crazy and am wondering if anyone has had a problem like this. I want to replace the ecm but I don't like throwing parts at a car to fix it. PLEASE HELP.