2000 Isuzu Amigo Idle problem

I have a 2000 Isuzu Amigo 4WD 3.2L that will sometimes idle correctly and sometime it will stall. When it starts to stall it runs at a low RPM it will fluctuate about 400 RPM, and sometimes it dies and other
times it ends up going back to the normal idle. I checked the Mass Air Flow sensor and that's not it. I was thinking the Throttle Position Sensor. Does anyone have any other ideas? Is there anything special I need to do to remove the TPS and clean it or replace it? The codes that I've gotten so far from the engine have been that the engine is running light or heavy on fuel.
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Check and clean Idle Air Control motor.
Check intake manifold gasket for leaks.
I'm guessing intake manifold... that would explain the ECM codes
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