Aaaah, Race Sh1ts.
I was also going to link in that Darkside Developments video but GVK beat me to it. The Parkins know their onions. They're good with petrol VAGs as well.
Manipulating injector/temp/maf/boost sensor signals is an absolute bodge. Steer well clear of plug-in boxes. Factory ECUs are more than capable of delivering the goods and who wants an extra box cable tied to their dash anyway?
The plug-in boxes are popular with leased cars because they don't flag TD1 warranty void codes, or leave any diagnostic breadcrumb trails, but people who know a bit more about mapping steer well clear of them