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When coming to a stop the engine does not go to a normal idle of 950 rpm, but goes to 300-400 stumbles and almost shuts-off. This started after head gasket replacement and head rebuild. I set the timing, and adjusted the throttle body per the FAQ and checked the idle and WOT switches per the FAQ (both work). It will start and idle OK, it runs really well under driving conditions. The problem occurs only when idle switch is activated. The kicker is I can disconnect the idle switch and it runs well, smoothly returns to idle (1000 - 1050 rpm). I am not sure what to check/adjust next. I appreciate your thoughts on this.

I had the same and it turned out to be a failing idle switch any way. Although when I tested it on the bench it worked just fine. It took me quite some time to get to this. I replaced it by another and the problem was gone.

This sounds exactly like what I had.

I'll replace the switch and let you know the results,,,Thanks for the input