I agree with the Reinhart comment regarding sound/tone. I have V&H Big Shot Duals; love the look and they are a bit louder than Reinhart. I wanted to retain the duals on my Road King Classic for the look but if I had a Street Glide I probably would have gone with Reinhart 2 in to 1 for a little bit better performance. I have several friends who run that system on their Ultras. You will also need a high flow air filter and a fuel management system. If you are only doing the pipes and air cleaner the V&H Fuelpak is a good one for the price and the Power Commader is also highly recommended if future work on the motor is anticipated. A lot also depends on what you want to spend. Reinharts true duals run over $300 more than the Big Shots and the PC about $100 more than the Fuelpak. The 2 in to 1 Reinhart runs about the same as the Big Shot system.