I've been reading the threads about walk a rounds for the o2 sensor. Am I suppose to put a spark plug non-foulers on both spots where the o2 sensors are? I do not have a cat. I bought truck with headers and someone has removed the cat and left the 2 on sensors .I bought the 2 packages of non foulers but do not understand witch one the front or back or both that I use them on. thanks Ron

 

You put the non fouler on the rear sensor. DO not put the non fouler on the front sensor.

 

Dont mess with the front O2 sensor it needs to read the exhaust to adjust while the engine is running just take out the post O2 sensor the one farthest away from the front of the truck and put in the fouler then O2 sensor

 

you must have a upstream 02 sensor.

 

Thanks all.. Gonna try it this evening!