Just bought a 2007 TS Limited noticed the basement looked dirty and also smelled exhaust<??
Looked it over, in the middle of the frame rails seen a lot of black on the wires and frame to find out there are the 2 steel frame rails that are tube steel appr. 3" x 5" that had NO spray in insulation which meant the radiator fan could blow the air from around the engine into the
basement..

Don't sound like a Spartan problem. But a TS lack of insulation at build out. Get spray foam and fill voids. Best solution I can think of with info provided. Rich

Got it done, It will be interesting to see if any other manufactures missed the same detail!!!!