I'm working on my 98 425, it starts and idels fine, when I rev it up it will miss sputter and backfire, and when I let off the throttle it dies but will restart. I've checked compression, fuel related problems, used inline spark tester, it has spark even when it is dies. I'm at a standstill, out of ideas, could it be the stator/ pickup getting week? Any help would be greatly appreciated

 

Check the exhaust lobe on the cam. Its probably worn off(especially if it backfires through the carb into the airbox)