You are not going to gain much by chip tuning a standard 1600.
I'm not too sure with a bmw, but if I wanted better performance from a 1600 I would rather look into getting a performance branch, freeflow exhaust and a performance air filter. Get reputable brands. This will give your car better performance and it will be fuel economic if driven normally.
Then have your car dyno tuned. Just by doing these 3 upgrades you could gain 10% more power.
Thanx