Ill start from the beginning.

I have a bad ujoint in my drive shaft. So I purchased a used drive shaft with 49,000 miles from Weber Bros Auto. I ship to to my buddys shop and have him install it. Its smooth up until about 40mph then terrible vibration starts. We cannot figure it out so we call the local indy audi shop. They say that I must have forgotten to put in the shims (spacers between center carrier bracket and body) Well either we lost the shims or more likely there were no shims in the first place. So we tried calling the dealer to see if we could buy some shims. They claim they have never heard of them and the shaft mounts directly to the body. So we are confused as hell. I ride down to the shop and they show me a diagram of the shims and there are marks on the old drive shaft where you can see where the shim was. So we try to use washers to space the drive shaft with no success. Still have TERRIBLE vibrations from the center of the car.

1. If there are shims where can I buy them?
2. If I can't buy them what size are they so I can make them?
3. If this isnt the problem at all, any idea what the problem is? Can the shaft be imbalanced?
4. If all else fails can I just take the ujoint from the new shaft and install it into the old shaft?
5. I am going insane I just want to fix this stupid car so I can sell the ****** thing! I hate it.

I am tempted to just install the old shaft and trade the car in for a loss, I have had nothing but problems with the car and am SOOO frustrated. If anyone has any diagrams or walk through please help me out!!!!