Smog failure for two years

Here is my story: I have this RV. It passed smog when I first bought it. Two years later I had to smog again and they found a low idle miss fire. My mechanic who has the AAA tag for excellence did everything and came up with the next and last solution of doing a 5,000 value job and said maybe that will fix it. $5,000 maybe. The cost was because it was a RV. Go figure. I took it to another place and it almost passed after tried to keep the idle up but the modules where not clearing and he said I need to drive it 400 miles and maybe that will help. I'm at a catch 22. I have been driving it illegally for three years now. I need a mechanic who know what to do. I live in Sacramento CA. Can you help me with someone or whatever. PS: The compression was also checked and it's at 150, and the mechanic did most everything you mentioned. There is always that but. I looked at your information but I'm not that good to follow it. Maybe you can direct me.