RV need help Chevrolet forum was a waste of time....

6.0 Chevy motors in my experience have an issue with wiping cam lobes. I would go through your standard missfire diagnosis with coils and plugs and what not but if you continue to have missfire codes on cylinder 7 pull the valve cover and check valve acutation and see if cylinder 7 matches the other cylinders Lift wise at the valve tip. Also check for a rocker being cracked. I know it's low miles but there was a hardening issue on those cams. I've seen them go 100k miles no issues and I've seen them go in 300 miles. I'd be willing to bet the previous owner was completely aware of the issue and thats why they unloaded it.