AudiWorld Forums - Vibration Issues... may have found the problem. Need some opinions

So I have posted before on the vibration issues I have, if you dont know here is a breif recap of the problem.

Driving to work, 10 minutes to get to the highway, on the highway for about 3 or 4 minutes. Slow down to merge onto the 404 form 401, and speed up again. Then I get this nasty vibration throughout the whole car. Its in the steering wheel, and alll throughout the car. If I put it in nuetral the vibration is still there. If I pull the hand brake, the vibration almost dissapears. Hammer on the brakes and it feels like I have badly warped rotors. Anyways vibration conitues for 2 minutes then simply goes away..... This happens like clockwork, it used to only happen once per week but now is every day.

It is not the pavement, trust me on this one.

So about a year ago the dealership took my spare and put it on the front right side, they said I had a bubble on the original tire. I asked them about the tread depth compared to the older tires, they said it was not a problem. After this I noticed the vibration. It only occured every week or twice a month. Now its there a lot. I think it is the difference in rolling diameter wreaking havoc on the Quatro system. Now that the 3 old tires are nearing the end of their life they wear quicker and I have noticed the problem more often.

My question is, have I done any permanent damage? Is this a fairly good explination of my perceived problem?

I sent the car into the dealship and they "could not reproduce the problem". They told me (a year ago) that the tread depth was not a problem.

Any suggestions would be greatly appreciated. I'm just out of waranty now, but I complained about this problem before the waranty ended.

Thanks