Originally Posted by ERinEC
I'm interested to know this as well. Do you just have the cats welded back on prior to the test?
This needs to be spelled out:
(1) Order the test pipes, go to your installation shop and have them cut your OEM cats out, then have them install the test pipes, then live with the smell (if any), then get a tune to maximize power, then enjoy the car for awhile
(2) If you are under warranty and you take it to the dealer for whatever reason and they see it, they could "black-list" your car depending on what future repair you might need
(3) If you are in Cali and concerned about the state smog test you either look to bribe the smog station (considered an illegal act) when the "time" comes or weld the cats back on and return the performance ECU tune back to stock so that you safely pass the test
(4) After passing the state smog test you go back to the shop to recut the cats out again and re-install the test pipes, then retune the ECU and you are good-to-go for 2 more years
(5) Repeat steps (3) and (4) every 2 years for as long as you own the car
For some people that's a small price to pay for the +25HP you will be enjoying inbetween the "welding cycles"
(As for me, I am not so sure)