As a rule if there are two ports on an external wastegate the top one is to hold it shut and the bottom one (nearest where the wastegate connects to the manifold) is to open it.

If you are running mechanical boost control then it is just the bottom one you want to connect to your pressure source with your boost control in the middle.

I'd only recommend using the top port in conjunction with more sophisticated electronic boost control.

Screamer pipes - unsilenced are f**king loud! Pretty much a no-no for track days unless you're only measured on static noise tests with a high limit such as 105dB etc.