I would use that rjc block off plate, and insert a freeze plug in the exhaust housing hole that the internal gate works off.
Usually down pipes leak in that area, so the freeze plug would be added insurance.
I too would go with the tial 44mm wastegate, make sure you DO NOT buy a fake one! if they are costing $150, your not getting a real tial gate. Plumb that bad boy off of the header, not off the exhaust housing if thats a t-netics. The header is the best way to go. If you have somebody competent to do plumbing, unless you do it, plumb the exhaust off the gate back into the down pipe. This will quiet it up completely. You can also dump it into atmosphere, the tial's are not too loud. I have found, if you dump it atmosphere, put a 90 deg. bend in the gate's exhaust pipe. If you go straight out of the gate with no bend, it is really loud.
hope that helps!