Have you gone through the basics I posted in #2 above? If so, anything there?
Think through this. You said that the engine runs well under 3000 rpm. You've eliminated the ECU, compression issues, and plug issues, so it is highly likely it's a fuel feed issue.
At higher rev's, the engine is trying to draw more fuel through the system and somewhere that fuel is either being blocked or air is getting into the system. Check all of the fuel lines for crimps. Check especially where the main fuel line enters the engine compartment through that big black grommet. Remove the top cover over that grommet to inspect both sides. It has been reported on this forum that corrosion builds up in that area and restricts the fuel line.
Get a clear plastic hose with the same inside diameter as the current fuel hose and run it from the primer bulb directly to the on board fuel water separator. Run the engine until it acts up and look for air bubbles. If none, run the clear plastic hose from the outlet on the LP fuel pump directly to the cut-off solenoid next to the LP fuel pump and repeat the procedure. Then, run that clear plastic hose directly to the LP fuel pump, bypassing the solenoid and repeat.
If nothing there, then test fuel pressure at the pressure relief bolt on top of the HP fuel filter cover. You will need a 6 mm adapter for your fuel gauge. Spec is 41 to 48 psi at idle with the vacuum line pulled off the regulator and clamped shut. There is a fuel screen on that pressure regulator return hose. Check that.
There is also a fuel screen on the bottom of the fuel pump insulator. It's a PITA to remove and if you do, have a new one on hand to replace it. See #29 at
https://www.boats.net/catalog/honda...225ak0-la-2007-and-later/vapor-separator-assy
Finally, there is a fuel screen on the port fuel rail. Check that and possibly replace. See #4 at:
https://www.boats.net/catalog/honda...bf225ak0-la-2007-and-later/fuel-pipe-injector