I just had a TON of maintenance work done on my baby, and even though I had just replaced the PCV and EGR valves before Moab, the service tech said that both of them where already full of carbon. This happened because I didn't clean out the tubes leading to both valves. The tech said that if the tubes aren't cleaned out every time you service the PCV and EGR they could get clogged with carbon again within as little as five miles (he may have been exagerating here, but the point was made).

So...if you're servicing your EGR or PCV, make sure to clean the tubes out too.