I purchased the exhaust $1250 + CA tax (the dealer will say it costs $1500+ but go to the BMW site and you will see the exhaust for $1250. So tell them that and they have to match that price) and was charged $450 for the install. The sound is fantastic. In sport mode it sounds great. In comfort it sounds good but due to lower revs the sound isn't as noticeable. It makes the car sound more like an M3. I love and think it is well worth the change. I didn't even keep the old exhaust and had my dealer to recycle it or whatever they do with used parts. The diameter if the tips are larger has a nice laser engraved M Performance on them.
As far as performance it's hard to tell but with less back pressure the engine breathes better so there should be some increase but specifically how much I haven idea. It sounds great so it therefore feels faster. Oh and the cold starts in the morning is awesome when your car is sitting in your garage. That's a great way to start any day.
Forget your Past but don't let it stop you. Tough times don't last. Tough people do.
1994 E36 Convertible (Inherited from my Loving Father)
2013 640i Gran Coupe
Carbon Black Metallic
Ivory White Nappa
Everything but B&O, Night Vision and Active Cruise Control.