this question if for a friend of mine. i went with the maggy hi-flow cats on my truck, with super 44's and my buddy loves the sound. he wants to do the same set-up, but he is worried about passing smog. when you get rid of the 4 cat system and replace it with two maggy's, do you mount your 02 sensors in front of or behind the new cats???? or is there something totally different he needs to do? ive never had mine smoged after changing out the cats, just curious if anyone had the answer to this one.

 

You don't do nothing, leave the O2's where they are. Magnaflow High Flows are emission compliant.