I wouldnt take the boost signal from where you are, id drill, tap and screw in a hose barb to your intercooler pipe just after the turbo, use new hose, run straight from the cooler pipe to the bottom of the gate. Unplug the top. That way you eliminate any chance of cracked pipes or hoses, and boost spikes.
If it still overboosts then theres a prob with your gate.
If it runs reasonable boost (whatever spring you have in the gate), then T off that line for your solonoid, similar to how it is now for the top part of the gate.