Perhaps I am a bit of a noob...but why would anyone want to run a tune when these engines already have a predisposition for carbon / soot build up?
The tune only accelerates the level of soot that will build up right?
Seems like the loss from a tune is greater than the gain. Sure you gain a few ponies..but you are in the dealer much more for service.
Unless you are the type running the tune while under warranty and will dump the car prior to 50k miles and pass on your sooty problem car to someone like me looking for a nice used one.