Okay I hope I will get an answer this time. I have a 03 civic dx 1.7l soch I have a set of headers from NOPI to put on I'm thinking cause the header is 2&1/4 that I should run 2&1/4 piping to the muffler. Is this right I plan on using a magnaflow muffler but I just want to be sure before I order it.

Thanks for the help

 

Yes you are correct except it's header not ers. But other than that a 2 1/4 on an SOHC would work.

 

sweet thanks

 

Also, make sure you have an o2 simulator because the cat is attached to the header on the 7th gen LX/DX (like the earlier Civics). 2.25" should be ok for piping, thats what the Magnaflow exhaust comes with so you should be fine.