The accumulation that causes restriction is usually right where the EGR pipe enters the lower manifold. The accumulation appears to be oil laden crankcase gases depositing their oil onto the hot EGR openning.
Most any way you attempt it you will send some of the carbon into the intake. If you saw the inside of the intake you would realize that the small amount that you could add will be inconsequential. If you are worried amount the stuff inside the manifold search for x66 in the archives.
Bosch Master, ASE Master, L1
33 years MB technician