I'm in the same boat as you mypatience so I thought I should respond to your post. Well as you have already discovered your options on a catback exhaust for a sedan are somewhat limited. One would think that the stock exhaust system for an LS coupe would be shorter than one for a sedan. If you were to buy a aftermarket catback for a coupe it would take some modification to fit a sedan. As there is a two inch difference between the two, the coupe being two inches shorter I believe.