I agree those carbs can be a bit of a nightmare, usually the waxstat idle control is to blame, as dubboy said if it revs pretty high when cold this is uaually the problem ( replacment wax stat are around ?20 for GSF )
The 1.8 carb is 90bhp but don't expect it to handle like a golf, the scirocco is one of those car's either you love em or hate em. shop around as i have seen them very cheap, but also ridiculously expensive.
I have had 2 and would definitly have another.