If it's J-reg Golf, that makes it a Mk3. In which case it's either the 2.0 8v engine or the 2.0 16v engine.
If it's a 2001 year Golf then it will be a Mk4 Golf, in which case it's only a 2.0 8v engine in a heavier car and it's unlikely you'll get much more power out of it.
So, is it J-reg or a 2001 reg ? Or a 2001 car with a private J reg plate on it?