I put a pair of K&N filters on my xs and ran into a carberation problem. I called Mike at Mike´s XS and he made some suggestions on jetting. It helpped but I still had a jetting problem, the carbs were running out of gas. Frustrated, I bought a set of 36mm Kiehn carbs. They were better. But the carbs were still running out of gas. I took the bike out and ran it until it quit, opened the gas cap and closed it. Started right up. I had a venting problem all along. The bigger carbs gave the motor a big hit of power everywhere. I´m still fiddling with the jetting. It has a flat spot right off idle. Have fun....jimi