i have a 1995 gmc, it is a half ton with a 5.0 305 v8. when you start the truck the idle goes from around 800 rpms to 1200 and jumps back and forth. When you put it in gear it will die or hesitate. It runs very rough and wont stay started. when you give it gas to speed up it acts like it is choking itself out. Now i have replaced the fuel filter, plugs, plug wires. distrubutor cap and rotor, timing chain and gears, map sensor, both temperature coolant sensors, egr valve and solenoid, idle air control, o2 sensor, catalatic convertor and muffler, injectors plus a view other things i cant remember. what else could it be. im at a loss. thank you very much

sounds like a bad vacuum leak, try spaying around gaskets and stuff with carb cleaner?

I have already replaced the gasket under the throttle body and changed a lot of the vacuums, I sprayed b12 around while started and nothing. I don't know I think I'm go an have to take it to a shop.