Audi Tacoma

My 2001 A8 at 29000 miles was taken to this dealer for a noise problem. Each time I took the car back for the same problem, only one mechanic said he both heard the noise and felt the viberation. I have had two customers ask what is that noise? At 30000 they replaced the both converters. I have had thousands of dollars of work done on this car and each time I have it in their shop I complain about the noise to no avail. One service manager told me that I had nothing to worry about as I had established the noise problem before the warranty ran out. When I told the new service manager this he said that unfortinately that service manager didnt' work there any more. I have all the work orders that state that there was a noise and viberation problem. There are two A8's one A6 and one A4 in my family and we are all goint to never buy another Audi and actually get rid of everyone. My A8 now has 50000 miles.