I bought a carsound cat, 4" diameter 22" long resonator and a 4x9 muffler. All this is 2.5" diameter piping. I figure it wont be too loud, but it is all strait thru... so im not for sure. It's hooked to my B18C with 12.5:1 CR.

thanks fellas,

-Nick-

 

I have 2.5" piping and 3" Carsound cat and same size Magnaflow muff and it's all pretty quiet. The only things that are loud are the secondary O2 sensor I didn't plug and lack of a gasket between cat and 4-1