IVAN93EG

i can hear something in my z6 head that sounds broken when i rev up. im still driving it but for some reason when im doing 70 mph in 3rd im only at like 3500rpm. i used to shift to 3rd at 70mph and be at like 5500rpm. it feels like its taking forever to go through 3rd and 4th. i just did the valve lash to specs because i thought something too loose might be making the noise but it was not the source of the sound. i also changed the timing belt and im sure its not off time.i plan on rebuilding the valvetrain as well as the pistons in the next two week any advice would help very much. thanx