Well I am assuming you mean a 1.8T motor. Please correct me if I am wrong about this. If so, about the only turbo you would fit on that manifol and still be able to manage properly by adjusting fuel and boost curves would be a K04. Some people like them, but I do not think it is a worthwile mod for most people. There are enough aftermarket bolt ons for the K03 these days that will produce the almost the same power for much less $$$ and I would rather do this than replace with a turbo that really is not that much faster and costs so much. You can read about probably themost popular K04 kit sold at www.awetuning.com
They also have proven to have serious reliability issues. On other boards, I have seen almost a dozen people that had bad K04's within the first 20k miles. Reliability of the little K03 has proven to be much longer on average.