i have a 97 cobra and i am running without cats...i have had issues in the past passing emissions so i bought a pair of O2 sensors and the MIL eliminators from american muscle. i know the car has 4 O2 sensors but i was told the the pre-cat sensors don't do much of anything. i am set to change out the post-cat O2 sensors and add the MIL eliminators so i was wondering if i should just go ahead and switch out all 4 sensors or just the post-cat ones...any suggestions?? :shrug: