Oops, I forgot to mention this
Check the idle air control (IAC) motor and passages. It's the 4 prong bugger on the left side of the throttle body. You can remove it, clean it (carefully) and check the pintle depth, s/b 1 1'8" base to tip (can you tell I've pulled mine a few times?
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Anoher possibility is the PCV valve and grommet.