Well, I guess from what I just heard that the Portland/ Metro area does do a testing when you renew your registration and your license. So if your vehicle doesn't pass inspection they impound your vehicle and sell it for parts.
Sucks that Oregon has finally started to do this but I guess it is inevitable. As for the propane setup, I have heard it is all in how you adjust the settings of the injectors and timing, best bet would be to call them and find out.