I had a set on my 1200 custom sportster. They were LOUD and there was little option to wearing plugs whilst riding. If removing the CAT (which on mine was within the OE exhausts) you definitely need to alter the fuelling . I used a SE pro tuner module and took mine to be properly set up on the dyno. With the Khromewerks and SE air filter, plus using the SE pro tuner, I got an extra 10BHP and about the same increase in torque, raising it from 72BHP to just over 80 and with about 74 lbs ft of torque. It made a huge difference to running and it went pretty well and fuelled brilliantly, more importantly, it ran a little cooler as it wasn't running so lean most of the time. However, they were very anti-social and way above what I would want on any bike now. Just too loud which made longer trips a bit of a chore.
