>I thought 99 XXX 9999 is possible. But it seem Vikipedia correct and me is wrong. Our biggest city is Istanbul and this table is formal: http://gib.gov.tr/fileadmin/user_upload/Plaka_Harf/Istanbul.htm
>
>I forgot vanity plates. I'm not sure if there is limitation about vanity plates, I saw much more longer vanity plates. I never thougt vanity plates at my applications and never got any feedback about it...

Same here, those plates have to be conform to the actual standards. However, we are allow to use the unused space so this gives us an extra number/letter to use.