i have used over the counter products from the local advance auto store, that you spray into the air inlets at the cowl, and they work pretty good. the trouble is the cause of the smell is mold growth due to incomplete drainage, and spraying stuff into the inlets doesn't fix the drainage problem. you'll have to re-spray every so often. i haven't gone to the trouble to find a way to fix the drain. mine doesn't bother me too much, and i'm lazy.