Mark,
You could go the 'girly' routhe like me, swap the air-filter element for a hi-performance ralli-art item, this improves the breathing slightly. Because you have kept the air-box no heat sheilding will be required.
I would say this option would be safer in filtration terms as well.
HKS Hiper muffler, is a good choice in exhaust, it will be my choice when I get some pennies togeather.
Then praps a de-cat and amp; turbo down pipe followed by the Ralli-art ecu.
All this should yeild around 340bhp.
If I was you, I would invest in a turbo boost gauge now and have it fitted prior to the mods - you will only have to do it later anyway.
Beware of t