I chose the vance and hines 2-1 pro pipe after researching other exhaust systems on the market. 2-1 systems seemed to put out best all around hp and very easy to tune with VH fuelpak. I did notice with the screaming eagle 90 degree big air kit, the base tunesuggested by VHwas too lean just off idle. Derek from VH tech support gave me a couple of mode # changes to make tune spot on. With the pro pipe and free flowing stock replacement filter, the suggested base map would be fine. The screming eagle 90 degree intake system flows a hell of alot more than I expected. Before aquiring the SE intake, I had a stock replacement K/N on order.My pipe came in before the filter, dealership qouted me a great price for the SE intake which they had in stock. So now I have still in the box, brand new K/N stock replacement. By the way, bike pulls very strong, gave it attitude that lives up to it's name.