E32 down pipes will not fit as is.. but, you need some cutting/welding job in right place. Best way is to do an exact E30 photo-copy job on the floor.... Also recommend to go for an Audi A4 rear box with dual exit tail pipes(they sound good too..sounds like you r having somthing big underneath). i'm using the entire pipes (cat by passed) from E32 except the rear box..
cheers and good luck