no it isnt, as long as you bring back the passenger side O2 sensor then you are fine. Since the back 2 sensors are your secondary ones and they are before the cats they really wont affect air/fuel ratio unlike some may say. I actually think that I get better gas mileage now. But yeah if you want the deep sound take them out but someone on here told me a great piece of advice. "If its a daily driver you may wanna keep them on cuz after your inital high from the sound, the cabin noise will catch up to u and can get a little irratating." But none the less I still love it. The only downside so far is now my parents know what time I get home at night

you did a gr8 job

Awesome job,very clean. :tup
My only concern would be if you had to drop the h pipe,you can't seperate it from the back half.:confused:

Well theres always our good buddy ZawZall....

Hey Torque, cant tell from pics but v6? or v8?
I've got 2000 v6 mustang convertible and thinking of either cat back or duals, can you tell me why you chose duals instea of catback? myself I like the duals, but do you lose gas mileage with duals, and now you have had on for over a year, still no codes?
Thanx