Seriously, that huge lump of steel hanging over the front axle doesn't exactly help your power to weight ratio. I am not aware of many tuning options for the engine itself, so just make sure it is well maintained to get the best out of it.
What you do have is a decent amount of torque, and the weight is a variable you can control. Remove any unnecessary weight, including the jack and spare tyre (make sure you have recovery and a can of tyre weld or similar). The back seat is not that heavy, so removing it will not yield too much in the way of power-to-weight improvements. The front seats however are ridiculously heavy, so if you chance upon an inexpensive pair of lightweight bucket seats, that will help.
Actually, one thing you can look into is some decent induction. This will not really increase the top end, but the less restrictive airflow will allow the turbo to spool up more freely, increasing low-end punch.