aparently since dono has the engine chipped etc, looking for cupra bumper / skirts etc. is trying to make it a look alike.
my advice as with all others, if you want more performance out your engine
like your air intake here then save up, get a less restrictive DP and CAT, or if you want to be extra cool get a bigger DP and scrap the CAT and go CATless.
but generally (without going stupid on the size) the bigger the area the exhaust fumes have to go down and the less bends and restrictions it comes across will mean better performance (but make sure you get back pressure!)
a plain back box will down nowt, apart from sound like a chav if you get a crap one that sounds like a wet fart going down the road .