Thats for Euro3 rated vehicles. I know here in oz our sprinters of that era are rated euro2 and are controlled by a CDI2 ecu, and they dont have injector classification requirements. I also know the same era om612 engine in my ml270 does need classification, because it is CDI2.5 and it has EGR, MAF and cats (still vacuum controlled turbo though). I think this is still Euro2 rated, but because its not a commercial vehicle it has different rules?
If your sprinter is like ours of that era, without EGR MAF and cats then I would say yours also doesnt support classification of injectors.
Whenbyou said the injector seats have been re-cut a few times, how much material has been removed? This could be why you got smoke. Usually you only recut if there is damage to the seat. Usually just a light scuff with emry is enough to clean the seat.