Engine struggling to rev high?

[LennysEleven]

I have a 90 325i and it seems like lately it has been having a harder time revving from 5000 to 6500. Seems like you really have to push it to get it up there, even when in neutral, what could be causing this?

thanks
Nick

[Erick]

maybe the throttle body is not opening all the way? I'm thinking air is being blocked at some point along the whole intake system....

I'm no expert mechanic though, so dont take my word for it.