There is another valve behind the pb unit called the deverter? flap, this changes air flow, if the leg flaps open they are ok, the fresh air flap behind the glove box default to recirc if bad.
If you pull the right panel on the trans tunnel you will find a row of vac. switch over valves, they seldem go bad but should be tested, then you can pull vac to each location from one spot to isolate your leak. You should get a vac. diagram they are all color coded.
jerryb