[christianchevell]

I would think no that it does not need a retune as high flow cats are that...no resistance felt. I would hope though you have kept the 02 sensors in the loop with no cats ..... the front ones usually get a delayed response code that you should have already had to alter in the tune so you should not need a retune. The rears get deleted in the tune but still remain in place and if they heat up... I dunno, some have asked before if they could delete the fronts...... and of course the answer is no, its what adjusts the AFR.....to go more toward Stoic ..... and if people being as they are have deleted the fronts they are well...... Nutso and asking for trouble IMO. Now cars have 4 o2s and not 2...... And the funny deal is:: its a ten thousand dollar per car fine for a shop to knowingly remove your cats....... If they were caught, so all these people who run catless... man they sure don't want anyone looking under their car for a traffic stop! Imagine that some cop gets bent and your in front of a judge who asks you who took off your cats? and you did not even replace with high flow cats....,( here in Oregon its legal to replace stock exhaust with headers), then judge sicks EPA on the shop.... you being so loud have a Fix it ticket for repairs or prove the sound is within such level... actually have seen a judge go out to parking lot to check and not accept a receipt as proof.... Its a mess, I would rather just run the HFC's as I do and live with it and change them out every 50k or so..... like check them every other time my springs are done.