Kind of a newbie here and I've read quite a bit of threads searching this. I'd like to know the real world performance of the various exhaust systems available on the market. On average I've seen people say that they add upwards of 10hp. Being a car novice for the most part, could someone send me to a page/document that describes how a better exhaust system equals better performance/HP? Also could someone point out the less noisy models, particularly for the P5s. I'm not intrested in making heads turn because they here a freaking high pitched buzz from miles away. Thanks

 

NO ehasut system will give more than 5 HP on a n/a engine! That's a fact! Most catback cost around $400. The axle-back or "Sport exhaust" that the dealer sells has been proven to give 2-3 HP and costs $200. Bottom line is:
1-n/a is expensive
2-exhaust do not do much for HP.

 

Well a new exhaust usually comes after you buy an intake., Since the intake lets more airflow in you need something to let it out otherwise you have too much back pressure in the system and that new intake isn't really helping as much. But its true that you may get only 10 hp altogether