As JB_UK said, weight plays an important role in how quick u can go from A to B.
Things you could do:
1. Remove back passenger seats;
2. Remove spare wheel(as said before)
3. Carbon Fibre Bucket Seats;
4. Remove door cards;
etc......
End of the day the car would look more like a
TRACK car which I dont think u want it to be!
With more power you would eventually end up getting a new clutch kit and flywheel as the standard might not be able to handle extra power.
Also another mod you could do is invest in a
BIGGER TURBO 
My car was 100bhp standard and is at 150bhp at the moment or 110kw 
