We'll See
I just had this done. For a four year old car, mine is probably about as clean as it gets. Canadian premium diesel with PowerService on every fill-up since I drove it off the lot, or if I'm driving in the US it gets a double dose.
Dealer: We offer this Terra Diesel Cleaning service for your fuel system and EGR, etc.
Me: Huh? This is a VW-sanctioned diesel cleaning service?
Dealer: Absolutely.
Me: And this will in no way harm my DPF?
Dealer: It will not, in fact it is good for your DPF.
Me: (thinking: ***? How can this be good for my DPF? Anyway, if anything goes wrong, I'm coming after them over it).
Me: Go ahead. Knock yourselves out.
You can find more info about the products and services here:
http://terraclean.net/service.php?ids=10
They did both the EGR and induction systems cleaning, and then they also applied the minor service (which is additives!!) to my fuel. I know this because not only was it on the invoice, but they had to get my key from me to unlock my fuel cap. To put a fine point on it: This is VW selling and recommending two different additives for your fuel...
I've kept track of the fuel economy of my car since it was new, so I will be able to tell you in a few months if it has made any difference in that respect. I know they are doing this because it makes them money (and they have invested in the equipment), but I'm wondering if a secondary reason is to minimize the number of warrantee claims on things like the HPFP. They get you to pay for the service and it reduces their risk.
As I said, time will tell. I don't mind being the Guinea Pig on this one.