1993 Jimmy hard start/poor idle hot

1993 Jimmy T15, 4.3L L35 engine (VIN W). Starts/idles fine cold. Hard to start hot. When hot, if you slow down and stop to park from any reasonable speed, shift into park, and release the regular break, it cycles in idle speed a few times (down below 400, then up to 700, then back) before stablizing. Similar effect but much less pronounced when stopped at a stop light with the engine in drive. Any idea on what the cause could be?

Checked PCV valve for vacuum, is fine, swapped with another new one as well, no change.

Linear EGR was replaced a few months ago by a local garage, after it suddenly had difficulty running (and starting), and MIL light came out almost immediately. This time, no MIL, and no stored codes either.

Engine seems to be running rich (from standing outside when running) at hot idle.

Also, when started cold with the hood open, I noted a bit of a sound from the alternator (a scratchy sound), but it is not very pronounced.