Why aren't they? Do they throw a code and if so, can't the code be tuned out? If they passed emissions with the comp cams making 80 hp, I don't see why the hot rod cams wouldn't pass, the hot rod cams doesn't even need springs. On the newer cars here in ohio, they check for engine codes. If there are none and your gas cap seals, you pass. On older cars,
(pre OB-II computer) they still stick the sniffer inside the tail pipe. We can even run LT headers, as long as we the cats and 02 sensor extensions so they don't throw a code. I don't know, maybe in places like cally and new jersey they tear your engine down and spec it, but most states just look for codes on OB-II computered vehicles.