I'm confused on the s13 hs header flange side

[Nismoking]

Okay I'm trying to figure out how I wanna layout an exhaust for an s13 coupe (change my mind on the fastback), and wanna throw a hs header somewhere in the pic. I first read in an old post that the flange was 2-1/4" (I'm guessing flange side), now I read in another post it has a 2.5" flange? Which is it, cause I can't determine what pipe size to use with out knowing if it will match the flange on the hs header exact.

Also anyone know a place that sells resonated test pipes with o2 bungs, and will it throw a cel (s13)?

Thanks,Chris

[Structure240sx]

just go with the bigger piping. idk about resonated test pipes but if u find one u can get an o2 bung to have welded in.

[Nismoking]

So if it's 2.5, don't bottle neck it by putting 2-1/4 inch piping on it?

Hey anyone know if megan racing has a 2.5" catback, and where u can get it. I don't plan on going turbo ever.

Thanks,Chris

[Structure240sx]

yea 2.5" is good for NA flows decent but u wont lose all ur back pressure