Almost certainly a 109G-6. I'll do a little digging and see if I can find more info on it.
EDIT:
The combat in question took place in the Strassbourg area at 12:30-12:45pm. I/JG5, II/JG53, and II/JG27 all appear to have been active in the area at the time. I/JG5 are the most likely suspects, as they appear to have been involved in some high altitude (8000m) combats with mustangs, and Anderson listed the altitude at 28,000ft in his after action report. All three of those Luftwaffe units were equipped with Bf109G-6s. Anderson's mustang was a P-51B-15-NA, likely equipped with the later V-1650-7 engine.
