Yes, carbs are synced and the motor is a fresh build with 18 hrs on it. I did do a leak down test a couple weeks to be certain everything was goodHave you checked the Throttle Butterflies to see if they are synchronized and fully open at Full Throttle?
Adjust Throttle Cable as needed.
I've seen Pump hooked-up 7600 rpm on a B-Mod Pipe with a different Yamaha based Engine. It's not the Pipe...
A fellow Rider has a Pump Gas Limited 760 with 46 mm Full Spectrums and B-Pipe and is pulling about 7300 rpm and doing about 54 mph...with NO PORTING
Maybe the Engine has an Air Leak?