Gutless above 4500rpm

[drburton]

I really think you need a more detailed description of the problem for anyone to accurately take a guess on the potential problem.

Is the 'slow creeping' at 4500 RPM happening in low gears too (ie 1st). Or is this just happening when you are in 5th trying to go over 100mph. Which, by the way you shouldn't be doing anyhow unless you are on a track.