Thank you all for your answers. This is exactly what I was looking for.

I ride an Indian Scout and I like performance, but I'm not looking to be a street-Rossi. I just want to change the exhaust note (I don't want it louder, just deeper) and improve the throttle response in the low end. The bike performs great and sounds good above 4k, but has a high pitch below that.

I know I can go with the V-Performance or J&H systems and get the paperwork, but the J&H is too loud in my opinion and I don't like the idea of paying 1,700 CHF for the v-performance.