Exhaust Smell from AC

I've noticed a distinct exhaust odor when running the AC in my 2000 LS V6. Any thoughts?

Have you checked for an exhaust leak in the engine compartment? The air inlet for the A/C system is at the base of the windshield.

Are you sure it's exhuast and not hot oil? If you have leaking valve cover gaskets (common) the leaking oil could be burning, causing a smell that you might think is similar to exhaust.

-Rod