The gains are pathetic and the MKIII has long enough of a stroke as it is. It's a complete waste of money.
From everything I've seen posted on all the various fourms that N/A generally comes in between the upper 140's and the lower 160's (at the wheels). Some people post results that are wildly higher, but almost all of them were tested using brands of dynos which are agreed by the masses to always report high and over optimistic results including DynoJet. In all actuality ALL dynos vary from eachother (even the same brand and model), they can ALL be skewed (the operator has a number of calibration adjustments available to him and the shop stands to make more money from you if you think every little change you make gets you big enough gains to merit yet another dyno run) and so on. The only way that dynos are reliable is if you ALWAYS use the same one; they don't change the software version; and you always have them run with NO corrections on.... you'll be thoroughly upset at the results, but the next time you dyno there you'll have a much more realistic idea of what gaind were made. Also, keep in mind that a car's measured output can vary by 10RWHP or so from one run to the next.
I dynod at 164RWHP on a very healthy N/A running a 3.5"GM MAF. This was untuned and running excessively rich. I don't think I would have done much better with a tighter tune though.
A guy I know pretty well in TN named Alex is running a fully built 7M-GE. .50 over forged pistons, BIG stroker kit, MAFT Pro running S/D (I helped him set it up, that's how we met... he's only the second person to get it running on a N/A), lightweight and balanced forged and cryod connecting rods, lightweight and balanced and bladed crank..... and so on. I think he's putting down 220, maybe as high as 240 at the wheels... that's pathetic given the total investment. He is happy with it though, so that's what matters.
http://forums.nasioc.com/forums/showthread.php?t=286440