I'd suspect that the heat shield washer was missing, installed incorrectly, or reused from a previous installation OR the injector was loose to cause that kind of buildup. Clean out the carbon, install a new heat shield washer, and see if you still have leaks.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)