ddyna... Technically and typically most FI systems adjust to the change of the mufflers well, if no change to the air/intake. I asked the service manager at my dealer about this when having work done on the Road King. He confirmed this is the case most of the time, but he has seen a situation or two where the FI did need tweaked even though slip-ons were the only change. I would give it a try. Go with the Python slip-ons only and see how it goes. If you have minor popping on decel this is OK, but if the popping is quite pronounced you might want to get the FI tweaked or chippped. Might as well go for the air cleaner then as well. HTH. Good to have you here.