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 had some noticeable pinging on my 2001 workhorse. The further I drove the worse it got. I got off the freeway and it stalled. Restarted no problem but had no power.
What I found was that the Cold Air Intake tube had worked its way off of the intake manifold/ throttle body. Once I reconnected it, the MH ran fine.
My point is: Just one more thing to check. Good luck