If you are a noob (and looks like it), I think the best solution here is to use the stock binary, underscale a bit and work with that. Once you figure your way around things you can decide if you want to do things "properly".
Your supercharger setup will most likely not be a high power setup which means the stock binary will probably work just fine without major mods. All the North American spec MK4 2.slows are wideband from the factory as well.
Hahaha how did you guess.... Joking. I know it's obvious.
I did initially think of using the stock ecu but I can't find any definitions for it. I've tried searching manually for maps but have had no luck. As you said I'm a noob so it's obviously beyond my capability.
I would even be willing to pay for a profesional Tuner to do it properly, however the ones I trust don't want to touch it as its a custom project and well out side of the normal over here.
So I only really have one choice and that's to try it myself using a well defined ecu that is allready programmed for boost and try to adapt it to work.
At a guess though I believe a stock 1.8t map will do exactly the same as what it's doing now.
I think the next step I'll do is log a standard 2.0 8v
Then try the displacement sum and log that
And after that I'll flash a stock 1.8t map and log that. I'll compare the logs from all 3 and see if I can learn anything from that