I have manually applied vacuum to the diaphragm to confirm that the cable moves when I do so, but beyond that I haven't seen anything under hood work at all. I don't think the system is getting that far to be honest. The most I can get out of it is the clicking of the relays when I hit the button. I also noticed that if I shift it into drive while holding the button down I hear another relay click, so I assume that both of them are working.
As far as the cable tension I did my best to match it with the throttle cable but I don't know if we've reached a point where that matters, yet.