The Audi TT LCA rear bushing is solid, rather than skeletonized (webbed) the
way the Golf/Jetta/GTI one is. It's less flexible than the OEM bushing, so it
improves steering precision and input.
Audi parts 5Q0-407-183-L & 81A-407-183 cross reference, but might not be
as stiff (but still stiffer than Golf OEM)