I purchased a 2003 Holiday Rambler Vacationer with a W22 Workhorse chassis and Chevy 8.1 engine. I have always had Ford 460 or V10 engines, so I am not real familiar with this one, so I seek your adv...
I agree with Scott bad gas (most likely sitting to long in the fuel tank). This happened to me earlier in the year. I have the same engine in my RV. I have a 50 gallon fuel tank so I went to Walmart and bought 3 cans of Stabil $6.94 per can and that treats 16 gallons of fuel, X3= 48 gallons and it solved the problem for me. I also put in 48 gallons of 92 octane fuel!