Yamaha f150 RPM loss

[Angelo190471]

I am working on a 2005 yamaha F150TRX and im not real sure what where to start on this one.
Just serviced, plugs, oil, filters, ect. A couple plugs where wet when I replaced (2 and 3 i believe). It has strong spark in all 4 cylinders on my spark board. It has 44 psi of fuel pressure on the rail with engine off.

When you floor it and hold it at wot, it will hit about 4800 rpms and stay there. After a minute or so the rpms will slowly start to drop. (throttle still wot) It will drop down to low 2k rpms after a couple minutes before we brought the throttle back. Bring it to idle and then back to wot and its fine again for a few minutes before doing the same.
The entire time the fuel pressure never dropped. Priming the ball didnt help.

when watching cdi meds. One thing I noticed is all the values would randomly spike in both directions for a second. All the cables are tight and no corrosion.
PXL_20210312_181332754 by Angelo Mehtala, on Flickr

Notice the min and max arrows.
PXL_20210313_165042918 by Angelo Mehtala, on Flickr

These next pictures are taken every few seconds as its losing rpms.

Right as we started to go

PXL_20210312_192936002 by Angelo Mehtala, on Flickr

PXL_20210312_193001248 by Angelo Mehtala, on Flickr

PXL_20210312_193105086 by Angelo Mehtala, on Flickr

notice intake temp
PXL_20210312_193053169 by Angelo Mehtala, on Flickr

PXL_20210312_193114367 by Angelo Mehtala, on Flickr

PXL_20210312_193135950 by Angelo Mehtala, on Flickr

PXL_20210312_193202147 by Angelo Mehtala, on Flickr

Any ideas on what to check? To me it seems like I have a bad ground, but i figured id ask before i start resistance checking all the grounds.

Angelo

[driver27]

I found my same year model F150 to be very sensitive to both the screen plugging in the vst tank, and also to injectors in need of cleaning. Ultrasonic cleaning will make a difference, external cleaning makes no difference. I believe that will restore your performance, properly propped, 6000 rpm should be easy.

[pstephens46]

Well...Just over 300 hours is not much running for a 15-16 year old motor. 90% of the time, this sort of issue is fuel related. Ethanol makes it worse if stored for long periods. Monitor fuel pressure when it starts to fail. That VST filter may become more obtructed as you run up and then pressure becomes harder to maintain. 4800rpm is way too low for WOT. Intake has to be loosened to get behind to the vst. Not too difficult if needed.

Edit: I guess you had the pressure guage attached to the rail while running. Cowl off I presume. Still points to fuel, IMO.

[Angelo190471]

yes cowl off. fuel pressure was fine the entire time at the rail so i think the vst is fine, but i suppose if the injectors are clogged it wont show on the pressure. Im going to get the injectors clean/flow tested and go from there.
as for the rpms his ptt switch doesnt work.