So, I picked up a new fuel filter, thinking "nothing to lose", since it might be time to change it anyway. Started it up, and after a moment or three of stumbling while it was getting the air out of the system, it now purrs like a kitten. Runs perfectly. So, I ran it about two hours to give it a workout.
Problem solved. So, I'll change the oil, oil filter, and air filter this weekend, and service will be done for another 150 hours or so. Unfortunately, I will eventually have to replace the EC-30, because it's the easy way to keep track of operating hours. It's just that the damn things are almost $300 bucks, and I'm trying to conserve cash right at the moment, and manage expenses on the motorhome, spreading them over time. I have an awning fabric to replace as well as an inside window shade to replace, and I'm trying to spread that out a bit.