I smell a rat!

[black_box]

I recently reawakened my '08 Box S after a year of slumber while I was working abroad. After a bunch of maintenance, including air and cabin filters, brakes, oil, and a MAF/throttle cleaning, she runs great.

I should also note that I dropped a plastic-handled screwdriver thru the engine compartment when cleaning the maf. I heard it fall onto the aluminum tray that sits down there. I couldn't reach it, so figured it would sort itself out on the highway or I'd get it when I have a chance to put her up on the lift.

There is, however, a problem: something smells baaaad when the car has warmed up.

I'm no expert, but it doesn't smell like burning clutch, brake, plastic, or oil. It smells fetid and organic (my girlfriend said "rotting pumpkin", but I thought it may've been a rodent that died somewhere, hence the title) but can only be detected when the vent is set to NOT recirculate or when the top is down (or from outside after stopping with hot engine). It takes about 10m of driving to warm things up enough to smell. I didn't notice it when idling for 10m from cold start. Turning the recirculate on seems to make it much better, as long as top is up.

I've thrown some moisture absorber packets behind the seat and a couple bags of activated charcoal to absorb the smell, but it's not really helping much.

Any ideas of where to look? I can likely use a lift sometime this weekend.