I may be wrong, but I believe the states are told by the federal govt how to handle emission standards, by basically threatening states with refusal of federal highway funds if states don't comply with federal guidelines. The states only started sniffer tests after being told to by the feds. States really have nothing to do with sniffer tests or obd diagnosis, other than complying with what they have been told to do. Rural states such as OK, probably have no pressure from the feds since there is nothing in OK, other than rolling hills and not many high population towns. The feds never go after small towns, just high population centers. I live in Tenn and where I live we have no tests because we are rural, but around all the big cities, they test, so if you live in a highly populated area, chances are you will be tested, and those tests are required by federal law. The states make the tests, but the feds call the shots as to when and where

 

well i am running a 2.50 in Y pipe to a 3 inch collector going to a 3 inch Hushpower muffler . I also have 2 O2 sims for the downstream O2s. the truck is running fine and i past inspection so its do able :P .