Bought Used RX8, Need advice

Howdy guys, I recently bought an RX8 at 98000 miles from a used car dealer. I know, that's terrible, but I got a steal. I am finding out why I got a steal though, and I'm wondering if they're sold it to me under false pretenses or are doing something shady and illegal. So it starts out with me buying it and needing it immediately, before it had taken emissions. They told me to take emissions and bring back the paperwork as soon as possible. I did so, and it failed emissions due to multiple misfires and a catalytic converter being inefficient. So I demanded that they pass the emissions and they complied because legally they have to. So I come back 2 days later and they said they replaced the Cat. Converter and it had passed emissions. I got the paperwork and confirmed, they did pass emissions. 3 minutes into driving it off the lot, the check engine light comes on. As you should all know, a car cannot pass emissions with the check engine light on. The codes were for misfires still, so I replaced the spark plugs myself to prevent having to back to those terrible people. After doing so, I expected the CEL to go away. It did not, and it read another misfire in "cylinder 2". While that would be simple in a normal car, there are no dang cylinders in these cars so it's reasonably impossible to tell exactly which ignition coil it was. At this point, I am calling the Used Dealership back but I don't want them to touch the car again, as they have no idea what they're doing with a rotary. I'm no genius, but it seems like they did something shady to get the CEL off and get the misfires to not register. Can anyone give me some advice on what to do and how to go about getting the repairs done by a Mazda Dealership and paid for by the used car place? Thank you

Bought Used RX8, Need advice