Q: Runs great when engine cold hesitates once warmed up

Engine rebuilt recently. When i get in the car in the morning or after it sits for a while when the engine is cold it will run great and rev high easily but once it warms up it starts to hesitate at mid rev and doesn’t want to rev high or go fast in any of the gears I have to up shift to go any faster it is not a problem with the catalytic converter either i think it’s a sensor do you have any ideas

My car has a manual transmission.