Well lets go ahead and see what ACTUALLY might make power on your car..shall we?

tb spacer, crap.
fuel rail, wtf kind of gain do you think this is gonna get you?
manifold gasket, negligible power gain at best
2.75" exhaust, ok thats an improvement. But you probably would have been fine with 2.5 so dont think the extra is helping you..just making you louder/more annoying.
injen intake. This by itself probably wouldnt net you more than 7hp anyway, because you cant take in more air if your not getting it out, so now we get to the header.

Just because one part adds a proven amount of power do NOT think that it just stacks up on top of each other. Each one can make an improvement when coupled with the other. You already gained a fair amount of horsepower to the wheels over stock, or are you not familiar with drivetrain loss? If a flash alone can get you over 200whp then be happy that the power could even be unlocked so simply.

So an intake header and exhaust gained you 10hp..now possibly you could see a little more from those specific components, perhaps theres more power to be made, but dont expect more than another 10 or so..