I have done on the roll accel tests with other mates running decats and mine was faster, on the higher RPM's decats catch up but not worh, besides you are doing more harm than good to the environment anyway.
Wasn't a test of the RS192 scorpion exhaust that showed that power wise there was 1bhp in favor of a decat but lower torque lowdown. If insist get a sports one, or a 182 one, which are best