I understand your post
! Been a rough go for a bit, who knows - maybe calm seas ahead!!
That being said, two thoughts:
1) If you have not yet changed the rubber fuel line to your generator, it could go bad on you and start air leaks, or at work, fuel leaks which could result in a fire. Yours, and my, era fuel lines were designed for pre ULSD fuels. They did not handle ULSD well. Note: This should not be the fuel line to the ISC, as that is most likely all metal tubing.
I replaced the rubber fuel lines to the generator and hydro hot, with Gates Barricade. But NAPA also has good fuel lines now. And almost anyone that you buy today, will be ULSD OK to use.
2) Yep, watch your lift pump. Ours is still the OEM unit, but for the same ULSD reasons, I feel it's not if, but when it will start to leak
! I do run fuel additive, Opti Lube, in each tank, and that might also help the Lift Pump.
The ISC is a good engine, and worth sorting out these problems, and when done - should easily go longer then your coach will hang together
!
OK, one last suggestion. If you have not yet changed over to Synthetic Automatic Transmission Fluid. Then starting the process now, would be a good idea. It takes a few changes to get it fully over...
Best to you,
Smitty