Paul the throttle position has more effect than RPM ; you'd need to know steady state, rolling on the throttle or booting it etc to sort this. 1/10th throttle at 5000 rpms is going to be on the pilot jet while full throttle at 2000 rpms is going to be on the main jet. (Note that there is more to it than this but basically you get the idea)
My guess is that your issue is in the transition between the pilot and the main, if you haven't already make sure all the passages are completely clear. It only takes a tiny bit of crud to,start causing issues..........if you have already done this, never mind.

Tom