1994 Chevy Full Size Blazer

My wild guess is that you have a vacuum leak somewhere.

Have you looked for any fault codes? What does it say?

Do you have any diagnostic instrumentation that can tell you what is working properly or do you prefer to replace parts randomly?

the code checker i have is for obd 2's and my blazer is obd1 i belive

Shoot it. Put it out of its misery.

If it is running rough or cutting out consistently at the same throttle position, and idles and runs fine after that throttle position, it is likely your throttle position sensor.

I like your answer also, but think the op has thrown a lot of parts at this already, and the TPS is not easy to diagnose for the everage DIYer.

Well, that's what internet auction sites are for. "Spares or repair" looks promising.

I have two suggestion. Well two that I can put in writing.

1) Look for the EGR valve. Remove the hose for it at the manifold source, and plug it and retest. If good, you have a vacuum leak, or an EGR valve that is opening too far or too fast.

2) If the vehicle is not good, look for the vacuum advance on the distributer. Remove the hose on it and plug the hose. Retest. If good, remove the distributer cap, and carefully inspect the two small wires that allow the stationary dist housing to connect to the movable pick-up plate. These wires tend to become brittle with age, and may have cracked the insulation from the movement of the vacuum advance. If the wires touch, it will cause erratic coil firing. The cure is replacement of the pick-up, but that requires removal of the distributer. This might be too complex, as it requires an accurate method to reset the timing and the actual pick-up replacement requires dismantling the distributer. Again it may be worth it to buy a rebuilt exchange distributer if you can handle the timing procedures.

3) It could be a coil breaking down under load. But, you say the engine works well at full throttle. Well, if you have an automatic, and the transmission drops into a lower gear (as it should at full throttle) then the load the engine sees is lowered. The easiest test for this is to wait till the engine is warm and soak JUST the ignition coil and retest. If it got worse, just buy and install a new coil.

Note If you did not change the coil wire, do that first. Good luck.