what is this?

[BL33SU]

http://s90139951.onlinehome.us/vw/diodemod.htm

got it from the diy section on vwforum.com

[MattyT]

It appears to be a bypass for the overboost safety feature of the engine. Getting rid of it is asking for trouble!

If you wanted to escape limp mode, probably time to invest in some kind of boost controller. There's loads around for Japanese turbo cars, not sure about European ones though.

[fuzion]

Probably just wise to save and get a chip done (Giac) or what not. Go for a run in someones chipped car to see the difference