I agree with Culzean. The DSI engine does not lend itself well to tuning. Air into the engine, and air out are not really bottle necks limiting the performance. You could spend a lot of money here and see negligible performance benefits.
Personally I would spend the time and money in keeping the vehicle as well maintained as possible. Perhaps do a deep service? New Oil, filters, spark plugs. gear box oil, coolant, maybe even the tappets. Not only will this have the engine performing at it's best you'll be keeping it running reliably for a long time.