I've gone through this a few times in the past, not with the Taurus, but older cars, and the one thing that helped, besides all the other advice you've already gotten is:
Lysol. The big old spray can, of what is now probably the "institutional" or actually "Professional" version (a quick Google found this:
http://www.staples.com/Professional-LYSOL-Disinfectant-Spray-Original-Scent-19-oz/product_445350 )
Start the car, open the hood, turn the heat on (not on MAX/recycle), turn the fan on as high as it goes, and leave the car doors open. Spray the Lysol liberally into the air intake (NOT THE ENGINE INTAKE, of course). If there's a cabin filter (which there is in the Taurus apparently), I'd remove it completely before doing this otherwise the Lysol will just wet the filter. On the other hand, it might **** whatever's living in the filter. I've gone so far as to empty half a can into the air intake.
I've done this in a few of my personal vehicles, and it immediately stopped whatever was growing in there. If I recall correctly, one of them needed two treatments, it was a 1982 Ford LTD.
Before doing this, however, wait for others to respond in this thread and make sure there's not some sensor or some other "gotcha" to this treatment method.
YMMV
