I went through twice without a problem. I have a Magnaflow catted X. I did have to flash my Xcal2 back to stock before I went so their scanner read my O2's.
yea 96 and up they plug into the OBD so as long as your check engine light isnt on they really wont say anything.... under 96 it gets the sniffer which is where you will be in trouble so your good like i said
depends on the year of the car. my 04 Cobra passed with L/T headers and hollowed out cats on my SLP Xpipe with an SLP loudmouth exhaust...as u can imagine it was LOUD.
Because after a certain year, they dont do a sniffer test on the car. what year is your car?