[miro_gt]

You would still need to get the internal gate welded shut, but I don't think the 15G uses a T3 flange. So you would need a differant turbo, but that's not always a bad thing.

or you can weld your external WG with a separate pipe on the internal WG port, and keep your stock GReddy manifold.

the 15G uses T25 flange

 

[miro_gt]

that one on the picture is Y8 block.

also, last time that same guy said that his WG keeps 11psi steady up to the read line

 

[miro_gt]

yes.

You can weld it up front in the middle, where the screw hole is.
You can weld it of the left runner.
You can weld it on the internal WG port.
You can make a spacer between the manifold and the turbo, and weld the WG on that spacer