the flanges are all ready turned on civics... if you get the jdm style dc you have to get the 2.5 in collector flange... but the integra ones have a straight flange, but if you order one for a type r the flanges match up but the stock one is smaller, if you take the cat off and cut it with a hack saw, nice and straight its no prob to weld and turn it...
are you talking about hy-techs drag or street header, there street header is desgind like the eday one i sent you in the other link, it gets 2 thumbs... but there drag header comes out thru the front bumper lol... def no street use... or very limited