that's your exhaust smell, the air movement brings it right back up to the cab, tips must be well out from under the truck, preferably aimed out or down ["just under the tailgate" looks more like a foot in from it] ... and those cute fat tips don't add anything to keeping the flow away from the truck, especially with a rear bumper ... like I said, exhaust is what comes out the pipe, not out of the engine compartment, unless you have audible leaks at the engine, "exhaust" smell in the cab is from poor system design
Bill
