Check the pick up in the distributor.
This is where the points use to be in the distributor.
I had a mopar performance unit start hitting in this area before and did the same kind of high rpm miss firing that you have.
Look for damage in this area.
I have a mallory unlite distributor, it is optical. the mopar performance unit is magnetic. but maybe it is the lamp in my ditributor that doesnt work under high pressure?
