Could be you now have a bent valve head. One of which tapped the top to a piston during that "Over-reving" sequence back a few days ago.

Or, (not likely) the clearances for the valve stem to guide got tighter and is slowing things down some.

Either way take a compression pressure check to see which (if any) cylinder may now be down a bit.

Car engines can still run good on 7 or 7 1/2 cylinders, but run better when all eight are firing off properly.

Not fun, and not cheap either, depending upon results.

Wm.

______________________________________
Old Ford owner