There are other ways to scratch a little more out of each setup, but it gets expensive for small gains. Larger exhaust will help, as will larger cooler piping/intercooler, at the expense of response. Porting the head and cams will gain some more power also, with the same response losses. If you want more power than that, it is usually suggested to jump a turbo size or two as it's cheaper, but everyone has a different setup, funds and goals.
The hassle is the stock rear housing, depending which one you have it will restrict the amount of airflow you can get out the back, thus limiting your power.