Brake parts cleaner. Wire brush. Tooth brush. Scrub a lot, run a can or two of brake parts cleaner through. I was able to clean mine out pretty well. Be sure to dump the pcv and the valve cover breather to a catch can or atmosphere and block off the EGR if you want it to stay clean. Might want to clean the intercooler (gasoline) and make sure your turbo isn't blowing oil too.