90 multiport 6cyl pontiac 6000 3.1

The idle seems like its stuck accelerating when decelerating slowing down stop & I dont come to a complete stop let of the brake the car will rapidly accelerate from almost 0 to 38mph Now If I actually have to come to a complete stop the Just about 1 second before I should come to a complete stop the idle will drop to about 1200rpm and litterally stop the vehicle and barely maintain an idle to keep from stalling and has stalled a cpl times. Have replaced TPS and new plugs and plug wires and disconnected & sprayed all plugs & connectors with electrical contact cleaner. car runs fine accept in stop & go traffic or having to come to a full stop. Any and all suggestion and help apreciated thank you

Throttle plate sticking? Bore dirty?

Possible IAC problem or Vac leak?