OK, I had forgotten about STI boost creep, so the order should probably be Wastegate port, flash, exhaust, flash... Somewhere in there, replaceing the stock paper filter with a high flow, snorkle mod(Does the STI have a snorkle?), and/or intake wouldn't hurt. Despite what Kevin thinks, intake is not just a new peice of pipe and a cone filter.
And exhaust can be as simple as gutting the down pipe all the way to full turbo back...