Regarding the stale air smells... if you'll look at the Idle-Aire system... and see how it is actually set up... you'll notice that each spot actually has it's own seperate Air Conditioner Unit. What is that pipe made of that puts that cool air down into your rig???
Plastic/Rubber like material... which does what? holds odors! The smell of exhaust... and naturally there's going to be smokers using these systems, and naturally some of that smoke smell and odors from their trucks will end up in that tube... that's probably where that smell is coming from.
if your a smoker, your going to smell smoker "like" air because everything in your truck that can hold odors... from your plastic dash parts to your cab curtains to your mattress... are all having cool air from a different source other than your truck being blown at them. AC in your rig comes from certain area's that your used to, AC from Idle-Aire comes from one big venting area, that your nose is not used to, therefore the air circulated is moved in a different way and naturally your going to pick up on odors your not used to... smoker or not.
I myself am a non-smoker, though I do pick up odors that I normally would not when I use the system... all simply due to a different air flow within the cab.