IMO, the TB isn't as much of a concern as the meter is, the stock TB should be about a 60mm, The stock meter is 55, that is extremely small, the meter should be the biggest.
I'd bet money that if you swap out the meter for a 75 or bigger pmas you notice a power gain.
I'd bet money that if you swap out the meter for a 75 or bigger pmas you notice a power gain.