Drilling hole in TURBO, wastegate question

[Tura_1JZ]

Hi, I just started getting my car together this year and I'm having a little boost spike 11-14 psi. The wastegate is new Turbonetics New Gen, it opens fine and holds 11 psi ( like it supposed to) until 4500 rpm then it creeps. The reference for the wastegate now is from intake manifold & t's off also to a tial blow-off. There is no leaking diaphragm because the top chamber has no vacuum. I was told to drill a hole by the turbo outlet then tap it to screw a fitting for wastegate reference. I'd like to get some opinions on this before I start poking holes on the turbo. Where exactly to make the whole? Is it necessary to even do this? Thanks, here are some pics.

 

[IJ.]

I always add a line to the IC Pipe just in front of the Turbo Coupler, makes life easier if you change Turbo's.

 

[Tura_1JZ]

So just tap the IC pipe then, does it matter that the IC pipe is thinner than actual housing itself? Will it hold the fitting firmly is what im asking

I always add a line to the IC Pipe just in front of the Turbo Coupler, makes life easier if you change Turbo's.

 

[IJ.]

I weld on a tapped bung when I do mine, can't see drilling and tapping being leakproof.