So theres a lot of information going around.

Does anyone know the difference between axle back and cat back? Do they both mess with the catalytic converter (Which is the main reason people fail smog)

From what I understand, anything that messes with the cats will fail smog

 

Neither of them mess with the cat, catback is after the cat, and axle back is just the mufflers(usually).

 

the only reason that people are saying catbacks and resonator removals will mess with your smog check, is because socal has a very strict visual inspection..

modified midpipes are not legal for ca smog inspections and i think axlebacks might even be pushing it.

 

im pretty sure you can do aftermarket hi flow cats. what they do to trick the system is they space the o2 sensors out on each cat, thats how we do it here in ny im not sure about the laws in cali

 

same in cali.. there are these things called anti-foulers/cel eliminator L bend things, that do the trick.

just attach the thing to the hole for the 02, then attach the o2 to the CEL Eliminator, and voila.. no cel

BUT, the main thing is, cali laws are so strict that they prohibit the use of aftermarket parts UNLESS you are given CARB legal stickers for the parts themselves.. ie, when i only had an exhaust on my tc, they wouldn't run my car because it was aftermarket even though it was just the axleback.

 

does deleting the resonators affect gas mileage and @ L3XOTIC u got 300 or 4? OP keep in mind a 400 will sound way different frm our 300's, so what may sound good on a 4 may not sound as great on ours.

 

has anyone here done an stock muffler delete, replacing with straight pipes and keeping resonator on a gs300?

 

Hello sir, just the other day, i heard a sound clip on youtube of a gs300 with the borla exhaust, and in my opinion it sounds perfect for my needs.