Hey everyone, was recently at my local dealer for the recall on the front passenger seat of my 2015 Sedona EX. Purchased an oil change bundle (which makes it cheaper to have done at the dealer rather than by me) and had that performed, along with a multi-point inspection. One of the issues that they pointed out with my Sedona is the need for what they refer to as a GDI service. I know that these direct-injection engines are more susceptible to carbon buildup but I'm unclear on what a proper GDI service entails. Do I just add some type of fuel additive that cleans the system out, or do I need to manually clean the carbon buildup off the valves? Thanks in advance for the help.