Well it must be for a mk3 then, maybe a ghia or something..but I can assure you its definately NOT an S1 or RSI skooshy water resovoir thingy...the S1 items were black, went into the wheel well through the inner wing:

Picture proof:


RSI:


You can just see it out of shot on the right...theirs no roomm for that washer bottle in either engine bay...ner ner Agree tho, it is from a mk3, just not any mk3 RS model