After carefully reading what everyone was attempting to diagnose, I could NOT find a solution to my Maxima (246,000+ miles). One thing that I did NOT do was to go out and just start replacing parts like the EGR valve, MAF sensor, Knock sensor, O2 sensors. I figured it had to be a vacuum leak somewhere but I didn't know how to check for a vacuum leak until I saw this video on YOUTUBE [
http://www.youtube.com/watch?v=9CPqbaSgcok]. This led me directly my problem, for convenience while searching for the EGR valve, Knock sensor, ... I didn't think to retighten the airbox, namely the brace ring behind the MAF sensor, which is where the leak was located. Once I tightened everything up like it's suppose to the problem was gone COMPLETELY! Nothing was wrong with the car. I had left the airbox loose. And the car was stalling cause of the leak while running RICH to overcompensate the added air coming from the leak. The car continued to run bias RICH for a couple of miles then switched over to running LEAN all by itself. Hope this helps anyone that's pulling their hair out.