I think you would be wasting cash trying to get it to go quicker, you would spend ££££ and not really get any gains that would feel noticeable.

You could chuck a bigger lump in but then you have to think of brakes etc and insurance.

Maybe a sports exhaust, decent filter and make sure the bushes etc are all good, lower it a little and make it handle well. It would be more rewarding, it is never going to be a straight line tarmac muncher so get it handling well and so it is more fun in the twisties.