"You probably overstressed the engine and broke something. Maybe a ring or a valve. Its not a good idea to beat the sh** out an old engine."

Haha, that's funny. What I've found is these engines like to be revved out and driven hard.. but that doesn't mean run them at redline or at the rev limiter for minutes at a time.

Maybe you just free'd up some carbon deposits that got lodged somewhere.. keep running it hard!