6Q was the SG 151 code but it seems that they didn’t follow the standard scheme. They made the third character the Staffel letter and the fourth the letter of the individual aircraft. Lovro Persen has written a book about 13./SG 151 in Yugoslavia: Guerrilla Nightmare.
If you want a list of SG 151 aircraft, I think you’ll have to compile your own but Persen’s book should help, also the Luftflotte 6 files for 1945 (free downloads from the Bundesarchiv in the RL7-6/ series). Also I collected a few here:
http://www.ghostbombers.com/NSG%209/communications.html