The recirc flap is part of the big black HVAC box that occupies the entire center of the car under the dashboard. That particular flap is roughly in line with the firewall, and runs the entire width of the heater box - about a foot wide. It is operated by two vacuum actuators, though there is only one flap.

It's possible to see a small portion of the recirc flap by removing the glovebox. Look past the pink vacuum actuator on the left (that's the defrost pod, BTW) more or less parallel to the firewall. You can see the rightmost bit of the recirc flap - most of it is blocked from view by the HVAC box. Try starting the car and switching the climate control between fresh and recirc while in the EC mode. You should be able to see the flap move. Better yet, get a mityvac and test each of the seven vacuum lines you see - this will tell you what works and what doesn't. All seven should hold vacuum. I recently suggested Larry perform this test, and have now caused him to blow his entire weekend pulling the dashboard out of his 300E.

You can also see the recirc flap by pulling the blower motor, but that's a bit more work...

- JimY