The EGR re-routes gases (including carbon) from the exhaust back into the intake, just behind the throttlebody. It fills the area with carbon and deposits get all over everything. That is why its gunked up and black all over the supercharger and inside of the throttlebody. Notice when you take the throttle body off there is a hole at the base of the supercharger with a tube sticking up through it. That goes from the EGR, follow down and you see the EGR pipe going from the LIM (Lower Intake Manifold) down to the Valve and then to the rear exhaust manifold. It sucks and it needs to be cleaned every now and then, but don't expect it to stay that way long.

This isn't going to be very much of your problem, just a typical thing you should be aware of.