Carbon deposit on Injectors

[zorin]

Hi,

Few weeks ago I took out the fuel injectors from my '88 260E (150K miles) to ckeck. I noticed that all had black deposit (carbon) on them, on top, the part that stays in cylinder head. I cleaned them with Carb Cleaner and put them back on. Does this mean my car runs rich even though the spark plugs are clean?
The injectors work ok otherwise.

Thanks.