o2 sensor vs. custom exhaust?

[SANDTRIBE]

Got a 1991 xj with 4.0 I'm looking to be making my own custom exhaust from header to tail end... my question is do I need to have my o2 sensor a certain physical distance on mt exhaUst or can it be anywere before the cat... I'm in cali so I gotta smog her when I get it going again...

 

[Tim_MN]

Put the O2 sensors in the same location as stock. An inch one way or the other shouldn't matter.

 

[jeeptec]

are you making the header or using an aftermarket header.remember anything in front of the cat has to carb exempt.(E.O. legal)that means the header and the head pipe also.