Not my work, but I found this very useful when I was messing around with my rear suspension. Credits go to dougyfresh (back when euroaddiction was still up) and blackjackT7 here on AZ. I have created a thread here for those that don't know how to search, and have also compiled a PDF of a web forum link that was no longer available. This information entails the process of replacing your rear control arm bushings and what to do if things go wrong. For those that don't know, all info from B6 A4 applies to B7 A4 as we share the same suspension. The PDF describes the process of removal of the rear subframe to remove the rear control arm toe eccentric bolt. There is a press fit nut on the subframe that with age gets loose making the bolt spin with the nut and impossible to get out.

LINK for rear control arm bushing replacement. LINK for PDF

NOTE: If the link for the PDF goes down just shoot me a email and I will get back to you or this thread.