I too had a problem with road noise in the cab coming from the right rear. What I did was to put some foam pipe rapping. The kind that comes in a tube and fits around the pipes to keep them from freezing. I pushed an 8" long piece between the cab and the bed to rest under the cabin vent. This has stopped the noise by about 90%. The problem is this material is not heat resistant and it is about 2 feet above the muffler and to the right. Moving, I don't think this is a problem but in a traffic jam where you are stopped for a length of time with the engine running, it might heat up and may catch on fire. I need some suggestions of what I can use in place of the foam pipe rapping.