No power at high RPM

[TheRealDannySavage]

So I've owned my GS for a month or so now and I've got to admit it is a blast to ride, but it seems now my bike doesn't want to rev up when it is under load.  It seems to rev to a certain RPM depending on which gear its in (7k-1st, 6k-2nd, 5k-3rd, etc.) however, it will happily rev past 10 grand without hesitation when its in neutral or clutch in.  I can't seem to find a straight answer online for my problem so I have decided to post here.  What is my problem and how do I fix it?

[mr72]

Could be any of a number of things, beginning with the slides not coming up on the carbs due to a vacuum leak, damaged diaphragm or other fault, or other fuel delivery issue like failing/clogged petcock, ill-advised fuel filter installation, kinked fuel line, or the carb vent hose facing forward.

I would just start with a carb once-over like my blog post suggests:
https://joshkarnes.blogspot.com/2017/09/fixing-common-gs500-carburetor-issues.html

If the issue doesn't resolve after you do that, then look for less likely causes.