IS runs good, but no higher end power

[Iswing]

Need help of Valkyrie experts.  I have 99 IS 23K miles.  Rebuilt carbs, new jets, new plugs, new timing belt.  Starts great, runs excellent. No problem at all if operating normal.  However, if you open her up as she gains RPMs it start to hesitate, wants to go, feels like it's trying, but like power reduction, kinda like a gas issue, but I don't think so.  Does not miss, I don't think its staving for gas, but not sure.  I believe the petcock has be replace.  Timing marks are correct.  Anyone have idea?  Many thanks. 

[Steel cowboy]

Check for cracked vacuum lines, the caps on the intake manifolds especially. Next I would look at the petcock, if the diaphragm is damaged or has a rip the fuel flow could be affected. Look into the vent line at the back of the tank if it's pinched the tank will develop a vacuum, open the gas cap and run it that way, to see. The vent line has a "T" fitting half way down, it's there for a reason, it allows the vent to work if you ride in the rain.

[Chrisj CMA]

The fact you said timing belt instead of belts tells me you sent it off to a dealer. The last bike I worked on that had carb work at a dealer. The tubes from the air box were not even hooked up on the left side. The K&N air filter was oiled on the wrong side and there were several torque issues on fasteners to be corrected. Terrible

[RonW]

As Steel cowboy stated, you might inspect the diagphram.

[3W-lonerider]

Need help of Valkyrie experts.  I have 99 IS 23K miles.  Rebuilt carbs, new jets, new plugs, new timing belt.  Starts great, runs excellent. No problem at all if operating normal.  However, if you open her up as she gains RPMs it start to hesitate, wants to go, feels like it's trying, but like power reduction, kinda like a gas issue, but I don't think so.  Does not miss, I don't think its staving for gas, but not sure.  I believe the petcock has be replace.  Timing marks are correct.  Anyone have idea?  Many thanks. 

also if you have a K&N air filter. check to make sure it isn't over oiled. if it is the bike will lose power anything above 4 grand. also a bad petcock will do that and the bike will not mis or run bad just won't have power above a certain rpm.