engine runs erratic at steady speed
Is the Check engine light on? Being that old, I would start by getting some throttle body cleaner and remove the throttle body, dismantle it and clean it. Remove the IAC, I don't think those you can tear down and clean. Looks like a sealed unit. You can try or buy a new one. Pull a couple of plugs. If they look black. I would replace your ECT.
Check for vacuum and boost leaks. Also check fuel pump operation. And fuel pressure.
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