ORIGINAL: KC36330
while it does sound like a pump it could also be a solenoid closing at high flow if plumbed in backward or anything between the pump and turbine, try disconnecting the tube from the turbine and test running the pump at various speeds and see if you see/hear a problem.
I concur with KC, sounds like solenoid not opening all the way and pump limit reached.
1) what is your pump limit currently set at?
2) on the ground, what's your pump pw at full RPM, if possible?
Sorry for your troubles,
Barry