Thanks guys. This discussion was very helpful.
The implementation would actually be on a v10 S6, so as Justin pointed out earlier, even more cylinders to worry about even distribution.
Would it be possible to drill/tap the manifold and install foggers right above each intake port?
Something like this for example: http://www.killerrons.com/drilling_tapping.cfm
Yes it would .
Exactly. If you did all that you would be in great shape. It would take a lot of work and these intakes are not made of the same material the ones shown in the link are but that makes a direct port approach and that works.
The manifold is actually made from simple aluminium . It was supposed to be made out of this sci fi magnesium alloy but turns out it isn’t . I drilled and tapped it pretty easily with hand tools .
The trick with magnesium alloy (the lighter kind) is that it heats up and lights up burning wildly.
Had first row seats to a guy trying to lighten kart wheels that were made from magnesium .
Needles to say the whole lathe was useless 20 min later . Burned right through it.
You can drill and tap it pretty easily. Be sure to use equal distribution distribution (haha) blocks .
I had a really good experience with wizards of nos.
The main problem with the S6/S8 v10 manifolds is that they are super rare to find used (none available globally at the moment), and about $2k to replace new http://www.ecstuning.com/Audi-C6_S6--V10_5.2L/ES145/ES286298/. I checked some dyno runs with the R8s and Lambos (those intakes are much more readily available), and their intake manifold designs sacrifice too much low end torque to make a swap worthwhile.
I had a chance to pickup a used S6 manifold cheap awhile ago, but passed. If I see another one come up for dirt cheap, then it might be fun to experiment on it. But at $2k each, there is no way Ill be drilling into mine anytime soon. I talked to someone who said they could likely do a JHM style plate system for about $2500 a pair. So, that would make a lot more sense if I wanted to go this route.
I wonder if some type of plate or direct port injection could be combined with an option to spray a bit of fuel or cleaner on the back of the valves regularly to prevent carbon build up.
NOS kit plus carbon cleaning all in one 
I’ve inquired about this a while back too. When Kryptonik had his PES blower installed he also had a w/m kit installed. The nozzles were situated similar to a port injection set up. They entered through the intake manifold near the bottom of the runners and I believe were angled to spray the back of the valves. I always wondered if an injector type cleaner was used either instead of or in conjunction with w/m if it would be a viable option to help mitigate carbon build up. A wild guess on my part but I’d assume it would be a fuel burn nightmare to tune for and too many potential variables to account for.
Yeah, I agree that the tune would likely be one of the tough parts.
I found this stuff online, that is supposed to clean your valves when mixed in with as little as 10L of gas
http://www.voltronic-germany.com/g20-valve-and-injector-cleaner.html
http://www.voltronic-germany.com/typo3temp/pics/16e55dae76.jpg
You mix it in with a tank every 5000 miles or so, and get sparkly clean valves (if you have injectors pointed at their backside of the valves).
If it actually worked like in the before/after pics, I was wondering if something could be setup where you mix the stuff in with a separate resevoir that just goes to the second set of injectors pointed at the back of the valves. Maybe the same injectors could be used in the wet NOS setup. And there would be a way to initiate a routine to run through the mix to do the cleaning, once the engine was brought up to temperature.
If it actually worked I would say a $3k-$3.5k price tag would be acceptable, since that is the price of about four or five carbon cleanings. Plus, you would have a NOS system at the same time.
I am sure it would be a lot more complicated than that, and who knows if that carbon cleaner stuff would actually work.
Just noticed at the bottom of their add
Products G22 and G23 apply with presurized device directly inject fuel injector network
Interesting