how did you make your Corsa sport 1.6 16v 152bhp?why dont you put a bigger engine in?
if thats not possible then...
bigger throttle body
cold air feed for the induction kit
lightened fly wheel
portand polish your head
its endless what you can do it just depends how deep your pockets are.
personally i would just get a bigger engine.
a car has a balance in the gear either fast aceleration or higher top speed, so buy putting a smaller box on it will scream when you get to a high speed.and alot of people put in the 1.7 puma in it and mount it to the 1.25 zetec box better power from the engine and quicker 0-60 from the box hes gonna keep the zetec-s engine in case anything goes wrong with the puma.