I only use this unit for trips to wilmington N,C which is about (320) miles roundtrip from my house about 5 times a year and to tailgate all NCSU home football games (50) miles round trip. It lasted 40,000 miles with the exhaust manifold on there. I think, but I did notice that some are bolts and some are studs did it come from factory that way , I would think not . do I still need to replace with headers, or resurface manifold , buy new manifold with stainless steel bolts. I also had class C that had exhaust leak issue but jut a short while when yu crank it up I sold it and never did anything to it but this one gets louder as it warms up opposite the class C