I know that with the older open loop EFI bikes ( pre '08 ), removing the cats made a performance and sound improvement! That is well documented. However, with the newer ( '08 and up ) closed loop EFI bikes what, I don't know what difference, if any, it makes. Reportedly, there is a slight loss of torque on the Vision when the cats are removed.
2011 Silver/black Vision, Ness Big Honkers, Ness Twin Sucker, PC-V w/AT, Lloydz VM1-DR cams, Lloydz Adj Intake, Lloydz Variable Timing Wheel.
2006 110" (133hp/142tq) +nitrous Kingpin (sold)