V8 3.6 Bj 89 only turns up to 4500U/min

Hello, have a 89er PT machine. It generally runs TOP and runs well, but it limits prematurely i.e. at 4500U/min. ==References====External links==*Official website ==References== Gang to 4700 or 4800 coming. Generally it remains with the 4500, but gradually it gets worse than before a time at least 5000 were possible! The whole thing comes abruptly abruptly and suddenly the performance is eliminated and it stutters like a loud and fast turning starter. A few months ago he was in the big service incl. two new cats, new end pot, new speed encoder, air filter as well as LMM and idle controller and other basic also NEW! Error reading was made and it was/is allegedly error-free. OT-Geber is as much as I know good and one still tapped on tooth wreath, flywheel or camshaft. In order not to do everything else, I ask for your experience and hope for help.
He runs up to this speed in any case super healthy and kernely - No, no, no! Thank you in advance. MfG Danny