Personally, I would look at the cam and springs. What cam and springs are installed?

You said you have a roller cam? As in? You could have a spring issue. Your symptoms sound alot like mine. Had bad inner valve springs and replaced them all with the correct springs, fixed a vacuum leak and ran like a raped ape.

I'll go into more detailed effects regarding mine later.

What heads, cam, springs, compression..etc. I agree with the fuel matter being rich, but a spring issue and vacuum leak will cause the same symptoms in the upper RPM band.