I took the intake manifold and crossover pipe off the car at 220K and took it to a machine shop. They soaked it in cleaner and a day later like new. It was caked on there pretty good. Plugged the egr to prevent this in the future and runs much better. Also replaced the intake manifold seal bc it was leaking due to time and sludge accumilation in the manifold. It cost me $30 to do, I recommend it.
1985 190E 2.3-16
1984 280GE Cabrio
1957 220S(running one day, I hope!)