Hmm stops pulling at 5000 rpm ..............had mine dyno'd, and the power curve dropped of a cliff at 5000 rpm, due to the fact that the car was running extremely LEAN, a very bad situation, and I would get the AFR checked so that if you are running lean you won't do any expensive damage.
One of Needswings/Waldigs fuel system upgrades has cured mine, just need to get back on the dyno with Eurocharged to solve a rich situation at WOT