Passing Denver emissions
 

I just bought an FD from out of state. The owner didn't need to pass an emissions test, so he removed the air pump and put a midpipe on. Any idea what I will need to do to pass Denver county emissions? I was thinking of purchasing a high flow cat, but I'm not sure if that will be enough with the air pump being gone. Since the car is coming from sea level I will have to retune it anyway, so if I have to put a cat and the air pump back on so be it. At this point though I am considering getting a PO Box outside of Denver and registering it there...

You'd need a working cat and an air pump. Without the air pump CO and HC levels will be too high.

Unless the car has a modified ECU, you shouldn't need to make any changes to tuning, Mazda has done that for you already.

The PO box thing doesn't work, from what I understand.

The ECU is not modified but has been "tuned" using a wideband sensor and PFC. My knowledge of Mazda ECUs and the PFC in general is very limited so I'm not quite sure what this means, but I'm fairly certain that it'll need a tune once it gets up here. Actually, this is the car:

https://www.rx7club.com/showthread.php?t=736166

Run it by the guys at Precision Import Repair and they'll help you figure out what you'll need to do.

Well...you can not give a PO box as your cars location, but you can give it as your mailing address. They will never mail anything to you except to the mailing address you certified upon registration...there are too many legal issues. They also do not check to see if you are keeping your car at that particular place. If you know someone in the springs or in Evergreen or anywhere outside the greater denver area, then just put there address as the place to register the car and then put a PO box as the mailing address. I told them that my FD is in the Springs at my aunts house. I put my mailing address my actual denver one, stating that I was in school in denver, but the car was in the springs (which is half true...like I would ever leave my precious FD in the springs).

PO Box does work! Just need a physical address to get one. PM me if you want to bring in a tuner to tune your car.