We are lucky to have the 130i here in UK although sadly no longer for sale in the UK market!
I am waiting to get a remap shortly but I'm only expecting no more than 15 bhp increase.
I think the Intake and Exhaust have more effect low down and mid range than at the top end.
PS I have read that the 125i/128i is just an ECU change away from the 130i so I think a remap will have greater benefits on the 125i/128i than on the slightly higher tuned 130i.