Probably lots of lag and money. You'd be better off getting a more suited turbo e.g. hybrid turbo but then again crazy money if you want big power gains (forged internals and a new gearbox etc.).
I have the same engine so I just made a custom intake (mainly for sound) and had mine remapped which is fun and decent bang for your buck (130hp for £300). If you want slightly more power, maybe a stage 2 could see 140-145 hp on a good day but anything more than that and you'd be better off just buying the 1.4tsi or cupra etc.