KAKI,
Surely, he was flying with JG 107, because JG 108 was only established in July 1943. See the links below:
http://www.ww2.dk/air/jagd/jg107.html
http://www.ww2.dk/air/jagd/jg108.html
Do you have any information about what kind of aircraft Ofw Hanns Stechmann was flying on this mission? Was he a later RK-träger?
Thanks
Adriano Baumgartner