Remove weight.
To get 10hp will cost nearly £1000.
To get 210hp its either throttle bodies or forced induction so around £4000.
They are pretty much as powerful as they can be out of the box.
Some re-engineered inlets, a decent panel filter, decat and a remap will make it breathe a bit better and will make it 'feel' better but is it worth £1000?? Not in my opinion, no.
I'd rather spend the money on a decent suspension set up and some proper tyres.