I had this problem with my C280, and cleaned the egr tube with a speedo cable attached to a drill, spinning to clean out the tube. However, after un-hooking the egr tube on the 'cold side'/ intake side of the motor I noticed that most of the build-up of resin was not in the tube itself, but in the passage into the breather. The hole was approx 1/2 the size it should be due to the build-up. Make sure to check this, you might clean the tube out and think you've solved the problem only to have it return soon after. I cleaned mine with a piece of a coat-hanger. Bending it over(tight) to make a small loop and then snipping the opposite ends(so your only working with around 4 inches-doubled). then file or grind the small loop into a flat spoon shape with sharp corners-be sure to put a small bend before the spoon end. You can use this tool to carefully pull out all the material. It might take a while with some patience.
I pulled out a bit then had a rag handy to wipe the tool off and continue until the hole was clean. If your carefull you can do it without pushing any material into the engine. I have had no problems since, my car runs great.