[ChrisBennet]

In case someone else comes across this thread with a lean-at-the-top RPM problem; there is another (unlikely) possibility:

If the fuel tank isn't venting properly you can get a lean problem at high RPM's. If the tank can't suck enough air in to replace the fuel it pumps out, a vacuum results that will reduce the ability to pump fuel.

If you hear a "whoosh" of air when you unscrew your gas cap, your tank isn't venting enough. At lower RPM's the fuel pump can keep up so you might not have any troubles until you get to the track.

Don't ask me how I know this...