I threw in some oil detergent, it didn't seem to help. I did a
compression test. All cylinders were just over 180PSI. On #3 the guage
needle wouldn't jump every couple strokes. It was missing the
compression. I guess a valve wasn't sealing properly or something.
Weird, I took the valve cover off again, and took both springs from
that cylinder out, and they both seemed fine. I guess the head has to
come off to check next.

I also ran the engine and took spark off each cylinder one at time, and
the noise did not change whatsoever on any cylinder. It's definetly
top-end.

One other curious thing is that the noise almost seems to float (in
pitch and volume) just above idle.

Any other help would be apreciated, thanks.