When I moved back to California I had to reregister my cars from Illinois. I self imported my '85 Porsche 930, and had a local shop do the DOT mods, they documented everything and added the cat, even the buzzer for the key in ignition. When the DMV sent me to their own inspection station, they determined that when the mod shop had the vin plate made they missed one letter, at that time vin numbers where not installed in European cars. Also did not install the fuel pump restricter unit in the gas pipe that prevented the larger non lead nozzle from being inserted. I then had to bring the car to the CHP, who kept it for a day to determine that it was not 'hot' and buy the restricter pipe and install it. I think that part from Porsche was about $300 because they where not happy about gray market cars. The people at DMV where doing their job, but as Gulf states above, we have all been through it.
I have other stories to share, from bringing in my wife's 300STD and having to take it to the station to determine it was a diesel, since at the time many people where pulling out the diesels from their Olds and Caddy's to a couple of more complicated ones...
Happy New Year...