Typical 1st post

so currently I'm looking for a mk4 golf gti and obviously after a little advice.
Had a quick blip in my mates 2l gti at the weekend and loved it apart from the engine which tbh felt V slow compared to our 2l Alfa 147. So I'm considering a 1.8t, think I need to have at least 1 turbo'd cr at some point.
Seems to be a huge range in prices etc. If I were get the standard 150bhp vs the 180bhp would it be a simple remap or am I right in thinking different engines etc can
gain different figures?
Found and viewed a mint 180 last night and loved it. Only thing that held me off was mileage. It's sat on the 124k mark but has history etc and belts etc changed. Anything major that can go wrong when it starts to clock mileage up?
Any advice or things to watch out for in viewings?
Thanks in advance