i have a 2000 a4 apr stage 3, it is misfiring under WOT. i replaced the spark plugs and it ran a little better but still sputters and misfires under wide open throttle. would my next place be to check coil packs or get a new maf sensor?? also after changing the spark plugs i took it out to see i the misfires were gone and pulling up to a stop light the car shut it self off and took a few tries to stay running. any help would be greatly appreciated!