To make you feel better, the gains you have posted are pretty much what to expect from putting a TMIC and a set of headers on.
I've always found putting headers on has decreased power, but increased torque. Have a look through and see threads where people have just put headers on. All sound disappointed as it doesn't make dick stroking dyno numbers.
TMIC doesn't create power.
3 port allows better boost control, as noted.
I think the engine design of the 08 is what is holding the car back from making big numbers (there's a reason the manifold is different between a STI and a WRX imo). Forgetting the numbers, the gains you are making are good.
As I have had to learn, don't get fixated on the dyno number. Bum dyno is the best indicator and most importantly does it put a smile on your dial...
Also, it is far more satisfying when your 200hp 'weapon' chops cars with much more 'power'
