What a minefield of a topic!
The standard exhaust is the twin pipes (to my mind, they look a little weedy in the cut-out rear section of the Aero 8).
The factory offer the side exit exhaust at £1,468.75 (GBP) and it should be noted, unless you ask them to fit a rear diffuser, your car will have a cut-out area at the rear with nothing in it (which imho, looks a little odd).
Another option is the Librands system -
as seen here - which is a quad pipe, rear exit, system.
As for the oval tips, like the Librands sport exhaust, this is an aftermarket fit item (if I am not mistaken) and I have not seen them on an S3/S4 Aero (only the S1 & S2). I am not sure who makes it but I am sure someone else will fill in the blanks. I know mr_tony has then fitted to his car, so perhaps he can tell us what the story behind them is?
