94yodamonster

I have a 94 v6 and runs strong starts fine but after being on the road for a few mins and i come to a stop clutch in the rpms dip down to right around 500 bounce around for a few seconds and return to normal. what would cause this its nothing to do w the brake booster it does it even w o using the brake pedal. If i am coming to a stop and i blip the throttle right before i stop the problem doesnt happen its just at slow speed. Any thoughts? input?