Engine Idle Problem

[Yukon92]

I am having issues with my 1992 Yukon with the 350/5.7l engine. After driving around for a few minutes (or on random days) i will come to a complete stop and the engine rpms will drop to bellow 200. I recently replaced the Air Idle Control Valve to try and solve the problem, this did not work. Ive come to the next conclusion of there being a ignition timing problem or a vacuum leak.






thank-you for any advice/help