We have annual diesel smogs here and biannual gas, so I only have to get my Jeep done ever other year. The diesel places charge more too.
I see guys in pickups with 16" dual stacks coming up the bed and I wonder how in the world they even get checked, although I asked a guy at a gas station once and he said his buddy owns a diesel shop and takes care of it... so likely the guys with the tricked out polluters skate the system somehow and the rest of us get shafted.
I am surprised that California is behind Colorado on this however...