From what I've read and have been told gutting the CAT will do very little for these engines. HI-FLOW cats (althought can improve performance by a very small amount) will cause CELS that can be ofcourse "fixed" with a resistor.
05 Matrix XR 4WD and 03 Vibe GT
"If you want Government to solve your problems, then you are the problem!" BMSR
Trix MODS: SRI w/ AEM filter, Vibrant/Magnaflow Cat-back, Alutec Lightweight Crank Pulley
GT MODS: Cosmo SRI, DRL, Auto Stop