Hi Steve
If you're holding out on chipping it, I could suggest a better breather filter (such as K&N, or similar) and a performance exhaust system - if that's actually available for your engine.
Fact is, that the easiest (and perhaps cheapest) gains for your engine can be had by altering the ECU. Also, instead of making it faster, consider modifying your brakes and suspension. Even if the engine remains the same, you'll be able to corner much faster, and brake a bit later than you normally would. Just a thought!
(it's also what I've been doing so far...)