Don, I'm not sure I would agree with this statement. There is a good possibility the fuel flow is not sufficient to keep the engine running at full speed. My wife's race car has done this same thing when she reaches the upper RPM range (8,000). In her case it was related to carburetor float levels being incorrect (blame me I'm her chief mechanic ).
In Grey Beard's case it could be fuel filter, partially plugged fuel line, weak fuel pump, etc.
As someone mentioned earlier the condenser could be suspect. I'm not overly thrilled with the quality of the aftermarket condensers. Something cheap and easy to replace to see if it helps.Brad