This mod uses an air intake pipe from the Seat Ibiza Cupra 1.9 TDi 160bhp (aka PD160 engine).
This larger intake pipe will fit all Fabia TDi based models and connects the cold air feed on the slam panel to the air box.
In comparison (see larger image) the Fabia pipe on the left, in this case a vRS version, is nearly half the diameter of the SEAT part.
The theory behind this is that the more air you can get into your engine, the better the combustion and in turn performance.
SEAT obviously thought it was necessary with the PD160 engine, so for a Fabia vRS with a remap it's pretty much essential if you are using the standard air box.