Looking for help with this yamaha. Engine runs very smooth up to 4200 RPM's. Anything higher and loses RPM. I am using yamaha diags while running engine. At 4200 the high pressure drops from 950PSI to as low as 10 PSI and engine barely stays running. I have checked LP pumps and medium pressure pumps. I have checked medium pressure directly at intake of high pressure pump. It never drops below 50 PSI. I've replaced the entire VST with a unit from a good running motor. I've removed the High pressure pump camshaft to inspect. All looks good. Engine has 86 total hours. Am I getting the wrong information from YDS. If I clear any faults and rerun engine until it fails, I get an injector fault and a low fuel pressure fault. Just for giggles I also swapped out both Injector Drivers and ohm tested all injectors. Can anybody tell me what to try next. Thank You.
