Diagram would be good of how you plumbed in your controller with external w/gate and the t piece .
I have plumbed mine in how I think is correct but loads of conflicting set ups on the net .

Mine goes
1,Cold side of turbo to small hole (spring and ball side of tee)
2,Big side of tee to spring and ball side of controller
3,out of big hole side of controller to the top nipple on w/gate
4, 90°off the tee straight to side nipple on the w/gate.
I take it the spring and ball act as a non return
Any help appreciated