I'm not sure how to measure performance increase but i will say the throttle response is better. If you like a deep sounding muffler this is the one. People know when you are coming and going no stealth mode with this muffler. The HD guys really like the sound so that speaks for itself.
I will be installing the sound core next weekend. I will post my findings after a test ride.
Also MBRP stands behind their product with a great warranty and has a very helpful and friendly staff...Dianna/support, Jeff/sales, Steve/shipping.