Back Box Delete 1.9 TDI 2009

[purevito]

Hi,

I own a 2009 Seat Leon MK2 1.9 TDI 105bh

I have an issue with the back box so I have decided to have the back box removed and replaced with a straight pipe,
I have been advised that this will not affect the sound unless something else is done but I'm not sure what that is, at
first he said DPF delete but then said my car is an older model, he mentioned something to do with the cat? can you
tell I'm a novice