Update....it is getting worse....but here is a little more info.

It is thumping just about everytime I start the car now. Turning the engine on and off makes no difference. That diaphragm module on the side of the vent structure...well it is sucking in and releasing fine, even though the thumping sound continues.

I just purchased the 5 cd set...and I have also purchased the complete 5 book manuals (the real factory service manuals) so I am hoping to get all the info I need to fix this problem. Please LORD...do NOT make me tear the dash apart....PLEASE