Disadvantes:
-The car will smoke as it doesn't have a DPF. Doens't affect you, only those behind you
-Extra load on a turbo known to be dodgy. The vast vast majority will be fine; but you've been warned
-If you pick a dodgy place to do it; they could do any kind of damage. Wait for a good personal recommendation
Advantages:
205-212bhp from 155 or so before the map (It' not 163, at least in the experience of the surrey readouts I've seen)
Therefore. Much. MUCH better to drive