Stock catalytic converters nowadays are actually pretty good, but if anything I would change to a hi-flow model instead of gutting your old one cuz gutting them will acutally create more backpressure in your system and cause you to lose power 9 times out of 10. when the exhaust gas comes out of a 2 1/4 inch pipe into a gutted cat that is 3-5 inches in diameter, it slows down the exhaust gas because of the larger space and creates the backpressure. Definitely not what you want