i apologize guys. i gave you misleading information. The O2s need mounted AFTER the hi-flow cats in order to work properly.

 

correction guys. i was not thinking clearly earlier. the magnaflow cats have a spot where the 02 sensor is mounted, so you will mount your original sensor in each cat. the dynatech cats that was posted in the page before does not have a spot for the sensor, so the O2s need mounted after the hi-flow cats in order to work properly. never drill a hole in a cat. you might need an extension if you are going to plug them into the cat, or O2's can be welded 6-8" behind the new cat location.

 

 

Also..... earlier there was mention that the 94106 cat has bungs already welded in for O2 sensors which is not correct. The 94106 will require bungs to be welded in behind the cat. I can't remember the part number of the cat with bungs already in them but it's best to just get the 94106 cats since the others still tend to throw a CEL on 04-08 models.

 

i just looked under my truck, i have 4 cats and 4 o2 sensors.
the first set of o2 sensors are mounted just past the manifold before the pre-cats.
the second set of o2 sensors are mounted in between the pre-cats and the cats.
so do i leave the first set of o2 sensors where they are and mount the second set of o2's in the bungs that are in the Maggie hi-flows? does this make sense??

 

they ones with the bungs in the cats are 94136, these are the ones i have

 

the first sensors are air:fuel ratio sensors. never touch those. thats weird to me about the o2 sensors being in between the pre cats and the stock cats. mine are in the rear cats themselves, but ive got an 03. honestly i would just leave them where they are when you get ur high flows put it.