Once you remove the EGR valve cover:
you twist a drill bit with your fingers to scrape out the carbon deposited in the top. I do not know how deep it goes. Many then recommend twisting pipe cleaners in there, although I worry about the fibers coming loose. We use pipe cleaners to clean our weapons in the Army. I think they are for cleaning tobacco pipes; I would definitely recommend these over craft ones, which are not designed for cleaning at all.
Unfortunately, you can get fat and\or long craft ones (that disintegrate easily), but a normal [tobacco] pipe cleaner is only about 6" long. I do not know how deep the carbon gets deposited and I used black pipe cleaners, but you could always try something like this "bore snake."
Coil Pipe Cleaner - Pipes and Cigars
There is much more information here:
http://ecomodder.com/forum/showthrea...-hx-22824.html
I should revise my first post to make it more comprehensive.