Power loss between 3/4000 rpm

[jakeschoppe]

2000 Chaparral 5.7 volvo penta. So our last trip off the water we began to experience power loss at higher rpm. When I brought it to an idle it would run. I could throttle up, but it would not sustain.
We changed the fuel filter on the water, but that didn't help. After reading and discussing with others I replaced both/entire fuel pump assembly. Took the boat out for a test run, and it starts and runs fine. Same issue however, as soon as I run for more than a minute on plane between 3/4000 rpm it looses power again?? Anyone have suggestions?

 

[dubs283]

fuel system restriction, what is the fuel pressure and vacuum?

ignition components could be suspect as well

 

[jakeschoppe]

Thanks. Checked fuel hose from tank. All was good. Pulled cover and got to the tank. Pulled pick up fuel tube. All good. Looked in fuel tank. Clean and no debris. Pulled exhaust bellows today just to double check for no restrictions. All was good. I'm still stumped??