Update on progress with this 803a - MOV installed over the weekend.
Also did some testing on a stove I picked up very cheap . With the oven door open and burners maxed out it was pulling 12.3kw and generator holding steady. 2 box fans blowing on the stove to help from overheating. Ran it for a couple hours just fine, then I heard the engine shut down and went out to check.
There were no error lights on, so I was figuring fuel issue. Checked output at the fuel pump and had nothing. Pulled the fuel pickup tonight and found it plugged up.
In case you are wondering how I got that out, I used a gear wrench with a bit adapter and ground down Phillips bit. I've used this same wrench for getting into tight places before, this is the first time I've had to grind down a bit.
Drained the fuel and didn't find anything else other than the drain tube was plugged up and a similar piece of slime eventually came out. Checked inside the tank with a scope, couldn't find anything else so I put it back together and changed the fuel filters. They had some gunk as well. These were the original filters, I never changed them because I figured something like this would happen and didn't want to change them twice.
Ran it briefly after changing the filters and everything seemed fine. Actually the Hz gauge was reading .5-1Hz higher. Spilled diesel fuel inside the generator pretty good and wiped up what I could followed up with engine degreaser and the hose. I'll let it dry out and should be able to test it again soon.