I had the exact same problem in a 1996 kodiak and also a GMC topkick (same kinds of trucks, I had two, now only one).
I had to replace little units, size of a thumb, I think that they were called TBI injector modules, cost about $160 each. I do not remember exactly what they were called.
I am not saying that this is what you need to do, your problem is with fuel delivery and you or your mechanic need to diagnose it properly. There are test kits out there that allow to make a proper diagnosis.
I am cutting and pasting below my notes from then. Perhaps you can find something useful.
TBI Injectors
Injectors or regulator assembly is leaking. It's dumping extra fuel into the engine.
Worn out camshaft - at least one lobe has "gone south"
I really want to thank you all for the info. but actually the tune up did fix the problem my dumb ^%$# had two plug wires crossed 5 and 7 thanks Mud puppy
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