150 HPDI RPM Problem

[GW Gulfstream 232]

My port motor sometimes will not go past 3500 RPM with 1/4 more throttle to go
I have no alarms I shut the motor off turn it back on and there are no problems.
It starts and runs smooth. Always 3500 rpm not lower or higher. Help Kevin

[Britfish]

I have the 200 HPDI, changed all the fuel filters this weekend including the one in the bottom of the VST tank. If you do it yourself, make sure you label your hoses, makes life easier putting it back together.