Back in 2009 I was nursing along a 1997 Audi A4 1.8t Quattro that I purchased from a private seller with about 175,000 miles on it. At that point I was unfamiliar with the complexities and nuances of the Quattro setup in these cars and what components wear first and what causes vibration.
After replacing the wheels and tires I corrected about half of the vibration issues and after replacing all of the CV axles on all four corners I still felt vibration and a certain motion during acceleration and deceleration. A quick search on the internet found that there is a two-piece driveshaft on these cars that is partially made of carbon fiber and that the car has a very sensitive balance element to it. I ordered the center joint and end joints and took it to a local VW specialist who does great things but he didn't have the tools to handle the job.
After a quick internet search I called Phoenix Rack n' Axle and was invited down the same day. I arrived at 11:00 AM and they quickly assessed my situation and said "no problem." A few hours later they had mounted all three joints correctly and had balanced the unit and had suggestions on how to align the center driveshaft yoke correctly to eliminate wobble. The car was as good as new afterwards and while the car was sold to a friend two years later it still drives perfectly nearly 120,000 miles later.