I added a factory rear spoiler to my '97 M3 Coupe, which came without one. The only compromise is that you end up with two "middle" brake lights, the one on the spoiler and the old one inside to rear window, (which is disconnected and no longer works). Of course, you could then spend the extra money to have the rear deck replaced without the "middle" brake light. I don't know what this would cost, but I didn't do it and no one has ever noticed it.