Went to the dealership the other day to hear a Tubi on one of their used Maserati's. The sound was incredible so I told them to put one on my car when it comes in next week. I found enough reason to buy it just for the sound that I forgot to ask if it will give any sort of power increase. I have searched online but have only come up with Dyno's down on Ferrari's and their was a significant power increase.
see you have an M3, Curious to how you like the sound of that car. I had an 2002 M3 SMG loved everything about that car except for the sound. Even after putting an after-market exhaust on it people at my work use to laugh at me as I drove away. Not sure if they were just breaking balls but it caused me to trade in the M3 for the Spyder.
My M3 has the stock exhaust and it is OK. However, my son-in-law also has one a '03 M3 (both M3s have 6 speeds) with a Borla exhaust. It is not nearly as impressive as the Tubi I heard on the 2004 Coupe.