A faulty downstream 02 can set off a cat efficiency code. I found 02 sims for our truck.www.thefastman.com sells them. Catless Y-pipe from the dealer and you're set. But you'll have to send me your old y-pipe w/ cats for some experimental testing!

 

Well I got it baack on Wednesday and no light yet this time they changed the rear O2 senser. Ok that the front one the cat and the rear. 3 third times the charm or 3 strikes your out any bets. How do i a pic