The current setup is  a 3 port Electronic controller being controlled by the ecu. I am using a Turbodsmart Tial external 38mm wastegate it had a 18psi spring in it. I'm looking at putting a 10 psi spring in it and tune the boost control per gear, TPS angle and rpm points. So in 2nd gear with throttle at 35% Ecu sets it at 12psi, but at 6000 rpm 100% throttle 14 psi, 3rd gear 15 to 21psi depends on rpm and tps points. As an example. That is why I was asking what's the best way. Intake chamber or close to the turbo for waste gate control.

In that case, always as close to the source of boost as possible.  If your compressor housing doesn't already have a nipple on it that you can use, get one welded on. :)

Also once you get to about double the psi of the spring you will also have trouble keeping boost stable