I know if you are wanting to clean the valves with this you will need to use the siphon method thru a vac port. As a fuel additive it will not touch the valves since fuel never touches them.
I've heard great things about this stuff actually working. My '07 GTI has 35,000 miles on it, never used any fuel system cleaner of any kind. I've read that it is a good idea to only use this stuff shortly before an oil change due to all of the contaminants it will dislodge, especially from the valves due to excessive carbon buildup common on this engine. Is there any truth to this? If the carbon and whatever other "buildup" is cleaned out, where exactly does it go? Does it harmlessly get burned off? Let me know what your experiences have been with BG products and how they are best used (directly into gas tank, etc).
Need VAG-COM work in CNY? PM me!