Welcome to the club. This litle pressure release valve works wonders for the car. As for your question about the voltmeter, make sure it's a high impedance one, say over 20,000 ohms per volt, 11 megohms per volt would be the best, and you will see the numbers change or the neegle move back and forth.

Don;t worry about the wastegate actuator diaphram, they are well made.

Make small changes to your setting. Unless you want the conn roda to break, stay away from detonation or knock, as it's called.

I carry a length of 1/4" fuel line in my car in case the G-valve goes bad.