1991 Evinrude E40ELEIA struggling at high RPM at times

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I have a 1991 Evinrude E40ELEIA that does not want to run at high RPM’s. It does fine at low RPM, and it sometimes does fine at high RPM. Randomly I will be at a high RPM then the motor loses almost all power and starts to pulse until I lower the throttle. I have cleaned the carbs and jets, replaced the batteries, replaced the fuel lines, replaced the fuel tank, replaced fuel pump, and replaced ignition coil. I’m not sure how to fix the issue unfortunately. One day I ran at high RPM’s for over an hour with no issues, then I turned the motor off for 2 minutes to test if it would struggle, once I turned the motor on it ran fine at low RPM, but as soon as I started throttling up it began to pulse and would not go into high RPM. Any suggestions?