1991 Pontiac Firebird started running ruff

For a car that has this low of milage I have had to do all kinds of things to it, I call it GMs junk.
Never the less, the engine was serging with rpms, before I tuned it up, if idling would run up and down from 700 to 2000 on the tach. Ok I did a tune up, noticed with the original distrubitor had a lot of carbon build up and rust, bought oem replacement, and a good brand of rotar with new cap, plug wires (9) mm, and a set of mgk plugs, gapped to specks, after I timed the engine to 1 degree btdc as specified. Engine cranked quick and easy, but the idle still hesitant, light accleration would go into a stall, more accleration would launch, full accleration acked like some plugs were missing out. Ok back to auto store, changed out Idle control valve, and egr valve. I don't mind spending the money I just want to get to the problem and get it right, fuel injection is a totally different ball game, and I don't want to waste much money unless have to. All vaccumm lines are replaced, the engine has no leaks, runs quite, just having accelator problems, and now it's hard for it to stay running at idle, simply you have to play with the gas peddle. I counted about 6 more sensors to go, should I purchase everything excluding the throttle body, and that's around $340.00. If your experienced with these 305 engines maybe you know this problem, and could help me out. I thank you for any response. Thanks, Mark Roberts
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