This has been a debate before. I think the biggest thing is how the motor runs with long tubes...something to do with exhaust pulses and the o2 sensors getting cold and making it run rich THUS making you fail emissions.
I think if it was tuned, with the cats and smog equipment, you should pass. Do long tubes fail the visual inspection though?
If your in CA and they see it they prob wont even test the car. But i've often wondered this myself. Because I've had muffler shops tell me Im not even supposed to run the high flow h-pipe with cats on my car even though it will pass emmissions with them on. So I think its all up to the shop that tests it. IMO if your car can pass the sniffer why the F do they even care what you have done to the car?? But the governator doesnt seem to agree.
I've passed the roller emissions test in DFW Texas for the past two years.
A lot of it depends on where you are located and it you have stuff that really stands out like off road mid pipe or stuff like air pump, egr and the like removed.
So it all depends on where its tested, it seems they would pass as long as you run cats and the smog equipment. I know some cams arent emissions friendly though.
I just passed CA emissions with all the mods in my sig. Minus the O/R X i put the stocker back on, and changed the Fuel pressure regulator back to the stock one too. I passed the sniffer by a mile. Im pretty sure any idiot smog guy knows that you cant have long tubes. If you can find a place that will over look that as long as you have cats that would be great. I just love how much room the stock H gives you even with a cam and heads and stuff.
So it all depends on where its tested, it seems they would pass as long as you run cats and the smog equipment. I know some cams arent emissions friendly though.
Why not just go down and talk to the guys at a local place and see what they have to say. Tell them about your car and just kinda get to know them.
All of the work on my car is done by me but I can't do the emissions inspection which Texas requires each year. I have had the same guys take care of that issue for the past several years. I get my work truck oil changes done at the same place also which helps them to know I give them what business I can. They know that the lt's on my Stang are not legal by the law but they see all the emissions stuff in place including the cat pipe so they pass it cause it runs clean when they run it through all of the tests.
I would look for a place that has some younger guys so they relate to what you are doing with your car.
It would not hurt if you picked a place that you saw had a Stang or two where the employees parked their cars.