Flapping noise in dash
 

Ever since I bought her, she has had constant flapping sound on the passenger side dashboard. Doesn't matter if I have the fan speed on low or high, heat or A/C or have it directed to the floor or vents, it's still the same constant, steady flapping noise.

Look for black pieces of foam in vent outlets. From what I've read it is not uncommon for the foam in the AC/heat control box to partially disintegrate w/age. I suspect that may be your issue. I had a similar issue and just pulled the flakes from the vents w/ hemostats to eliminate the noise. Heat and a/c still perform well so I have not tackled the real fix of digging into control box (big job).

It might be that if there is some foam stuck in the way of the door closing all the way.

From some research that I've done which relates to some other cars, a small door isn't closing, either it's blocked from closing or a solenoid isn't working properly. If it's the later, then I think the whole dash would need to be removed to get at it.