You can add a turbo back exhaust, replace the boost pipes etc but you won't see any power gains if any at all
All you can do is to ensure it has as close to the factory quoted power of 150bhp as you can so regular servicing, replace spark plugs, coil packs and any perished pipes etc
If you have any tiny faults on your car when you come to remap, the remap will multiply the problem 10 fold and you won't see the true potential of the remap