For a Port injection engine, there will be no intake valve coking, the benefits are reduced knock retard, etc.
For the LLT and LFX V6, then at 90k your valves will need a manual intake valve cleaning, and then get a proper can on it ASAP. Search here for a few threads on the cleaning process, and do NOT do a seafoam or similar as damage will occur with a GDI engine due to the deposits being a baked on crystalline make up that is as abrasive as sand when it sheds.
