Sorry, intake plenum is the name for the uh..."black tubing" that goes from the air box to the TB. No you do not remove the TB. The water valve is just underneath that.
Part #27 (the huge long thing), comes off attached to the upper housing of the airbox Part #1 as one piece.
The water valve is just underneath that, part #1 (it will be black). Trust me, it's very easy and worth a shot. The picture is flipped so don't let it confuse you.
I might be able to meet you somewhere in town and show you, I won't do it because it'll be hot as hell to touch that valve, I did mine on a cold engine.