Originally Posted by Reaxions

What kind of injector cleaner are they dumping in your tank? If you're using Premium fuel, it's my understanding that it shouldn't really need anything else added. If you are using Premium, it's likely that the carbon buildup would be on top of the valves, as our cars are dfi and the detergents don't wash over the tops of the valves (as they do in non-dfi). I think they have to be either manually cleaned, or you could maybe spray some Sea Foam directly into your air intake before an oil change. That type of top-of-valve carbon buildup is apparently very problematic in Audi dfi's and a few other makes, but I was told by one of the Jag techs that because of our engine's dfi design, it hasn't really been too much of an issue.