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I'm putting an hp header(an high flow cat) on an 03 HX,it came off the same year EX,has any body not used the o2 sim. with this cuz i don't have one yet an i'm doing it anyway,i would just like some feedback on this. Will this acually make my exhaust louder its a 4-1 race header i'm looking to make some sound out of my skunk 2 exhaust.........

 
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louder but not any more power

 
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not using an 02 sim you will probally throw cel