[philinjax]

The symptom you describe is fuel starvation at power/high rpm, all okey otherwise. Check the little sock fuel strainer in the fuel feed line
fitting which protrudes into the tank. The strainer screen is so fine that it can easily clog up with varnish restricting fuel flow.

You will likely have to pull the fuel tank to check this. One time, I had a skinny armed buddy stick his arm down into the tank (after I had pulled the 8 bolt top cover) and simply pull the screen off the fitting. Worked like a champ, but I don't recommend it.

Phil