As its designed for the mk3 i wouldnt have thought it would fit.
Also i believe that on the mk4
cupra, the pipework enters the inlet manifold from the offside, but on the mk3
cupra, it enters from the nearside, meaning the pipe run would be in completely the wrong place.
If you were to fit a mk3 mani (possible?) then you could run this setup but for the sake of it you might as well just buy the seat sport setup with forge pipework.