2005 yamaha 90 4-stroke weird issue

[will941s]

My 2005 yamaha 90 four stroke died on me a few days ago. Would not stay running. Pulled it home and changed filters and cleaned out the VST box which was full of crud. Put it back together and it starts and runs good but seems to surge a little. Like maybe 50-100 RPM drops then picks back up. If i unplug the vac hose going to the fuel pressure regulator it seems to do alot better. Plug it back in the surging starts back up. Any ideas on what's going on here?? Low pressure pump is putting out 10 PSI, didn't get a reading on the VST

 

[99yam40]

Re: 2005 yamaha 90 4-stroke weird issue

need to get reading on rail pressure too so you have an idea of what all pressures are doing.
Injectors have small screens in them too that will plug.

Make sure all screens and filters are clean, monitoring pressures should show if there is a restriction and if regulator is doing it's thing properly