besides sounding like shit and being illegal, gutting cats will make a nice expansion chamber in your exhaust, letting your exhaust gasses expand and cool down, slowing the flow and making even MORE backpressure than before, thus hurting your power in the end. modern day cats are high flow anyways, they dont hamper exhaust flow as much as many people seem to believe. the honeycomb design is the same as the aftermarket high flow cats and is much better than the old, restrictive plate-type cats. in short, take them off completely, which is still illegal, or do nothing. you probly wont gain a whole lot of power anyways on an otherwise stock engine (i dont know your mods though).