I suspect its TADTS as mine does as well. Could be the way the engine is mounted, road cars tend to have a third top link I don`t go to max rpm. the power curve drops quite rapidly above 7k `Short shifting` at 6800 gets you there quicker. Stress goes up as the square of rpm., 6800 to 7500 is about 23% more stress. The engine may have the Ford flywheel and be balanced to production tolerances which don`t anticipate 7500rpm And then there`s.........!!! Let us know what you find, if anything