I've learned so much these past few months after being hired on by kia as a technician. One thing I've been seeing on these GDI engines is extreme carbon buildup on the intake side and even the tops of the pistons at mileage as low as 15k. Well one of the main causes of this is the dreaded recirculation hose off the cam cover. This carries air with oil contaminates back into the air intake pipe. So on my personal car I added a high flow mini air filter on the end of that hose instead of running it back into the intake. Now doing this has now made my car a little more impractical, this mini filter gets diry pretty quickly but it's the only thing I can think of..What do you guys think? You guys have any ideas?