I just diagnose mine and fix it two days ago, thing is my only rev to 450-500 rpm at idle, when u rev it up it stumble to 100rpm and almost die, sometime it die. aafter checking, for leaks,replace egr,intake gasket ,injector,throttle body,plugs,wires, and vaf. it still does the same. then i parked the car for 2 weeks, came back to it on sunday,replace fuel filter since i havent in 7 years. and still no luck.
then im about to give up. i took the ecu off my other car,plug it in and baaam, the car runs and idle at 850rpm, so check /replace your ecu to see if thats the problem.
