hey sunsetaz i live in mesa,az. i have not gone through emissions yet i am recently out of the army and still have my plates from tn. but as long as the cats do not cause your check engine light on. the other reason we need all four is because they are "supposed" to visually check that you have all four cats. thats why people gut them. im not guttin my new cats. i payed in the 400-500 dollar range fo everything except my muffler. contact me if you are looking at having it done. i was gettin 600-1400 dollar quotes to have my exhaust done. i only price checked to compare, i always use the same shop