It boggles my mind how inspection stations get away with this. I truly think it is a combination of ignorant and uneducated techs that regurgitate information without actually knowing anything. For starters, light duty (for the idiots in the world that is K30, K3500, F350, 3500 or anything else with the number 3 or lower in the weight class designation) diesel pickups did not have cats just up to the last few years. To my knowledge, the truck either has no cats or a full particulate and sulphur system. I am unaware of any domestic light duty diesel with a traditional oxidation and reduction cat like a conventional gasser. Someone please correct me if I am wrong. That means that unless it is a fairly shiny new rig, it needs nothing more than a very long straight pipe with a muffler somewhere in between. For technicians to think anything otherwise to me is freakin' ridiculous.
I'm sure that when these morons get out of line and have a hard time reading the federal emissions label which clearly indicates what the truck needs to have on it or the phrase "emissions exempt", a quick snapshot of the numbers on the inspection station along with the "I wonder how the local police station and state DOT would feel about you not following the book" would net you a nice new sticker on the windshield.
For a decade I taught auto tech at secondary and post secondary levels. I've spoken to many people in the field and everyone tells me cars fail if the TPMS light is on or the car has no sensors in the rims. No one could actually show me where in the book it said that. They ALL just assume that if the car has a warning light and it is illuminated, the vehicle fails. That great Timmy, but lets inspect the vehicle to state standards and not to how you feel it should be.
Sucks that consumers need to be the ones educating the inspectors...almost makes the system completely useless and just a money maker...