I'm no lawyer and don't claim to understand government interaction in our daily lives, but whether or not a big or small group would be effected by this enforcing, giving the EPA any power to regulate our hobby would restrict racing in the future to some degree and lets them get a foot in the door for further regulation.
My 79 Cutlass came with a cat which "fell off" many moons ago. My son's 78 Cutlass came with a cat and an air pump, both also fell off. So despite our area not requiring an emissions test, it seems according to the EPA neither car should be allowed to drive on the road or a race track.
What about late model race cars? According to what I've read even reflashing the computer because you changed your exhaust system or cam or whatever is illegal. Imagine what people are doing with late model muscle cars to run in certain race classes. Apparently every bit illegal and the vehicle's owners at any point could be fined. What??
I reiterate what has been said, if this wasn't something we should be concerned about then why is SEMA getting involved in a very active way? My guess is it's costly for them to get involved so if they're willing to spend the cash and time to push back against the EPA then we should probably keep an eye on it too.
I signed the petition as well, I prefer dogs over cats and so does my car.

Speedtech as a group supports SEMA's decision to make sure the EPA's intentions won't lead to restricting what we do.