Hello every1,

what inch piping should I use for my exhaust (custom made)?

-with cat (OEM)
-without cat (with cat-replacement-pipe)

I donīt carry much about the sound, all I want is performance...

 

are you going to put turbo on? if not then 2 1/4 but if you are then 2 1/2 or larger. weather or not you keep you stock cat is up to you.

 

If you go with a mandrel bent system, then a 2.25" should do fine.

If you go with a Crush bent system, go to 2.5" piping.

If you can, save your pennies for headers, flex pipe, and a high flow cat. Then get it all done at the same time, in the same diameter.

For example, HVE 4-1's and SR 4-2-1 headers end in a 2.5" collector. So go with a 2.5" flex pipe and high flow cat. The SR 4-1 headers are 2.25" or 2.125, so go with a 2.25" flex pipe and high flow cat.