Ford Repair: Ford Explorer Stall Problem, mass airflow sensor, vacuum leak

Question
I have a 1999 Ford Explorer w/ a 4L SOHC engine & 115,000 miles. It starts & idles fine until it's dropped into gear, and it dies. It promptly restarts, drop into gear & goes w/ no problem. This is a cold start problem. It's almost like something has to "reset" before it runs properly. It does not trigger a check engine light. I have previously replaced the upper & lower intake gaskets & it ran fine after that. I have checked & cleaned the idle air intake valve, it looks fine. Your thoughts would be appreciated.

Answer
have it smoke tested cold for a small vacuum leak-i know you replaced gaskets but these are notorious for sealing rings leaking cold then seal off within a few seconds then they are ok for the rest of the day or until it sets for several hours.

also check mass airflow sensor for dirty filaments and it doesn't take much. good luck.