If you need a new cat, just get a random tech one. Its increased flow usually ads a couple HP, but as mentioned, you will lose a bit of torque, due to the loss in backpressure....Also, ridding of it makes your exhaust loud and freakin annoying. I know cuz i know a couple people that have done it, and i will never do it after hearing their cars!!!
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Ryan Walsh, 1997 200sx SE-R w/ ES mounts, JWT s4's, AEBS 4-1, PR CAI, Greddy cat-back, Sportlines/AGX's, Bridgestone re730's, Stillen GTR grill