boost leak test,valves no overlap question

[stomp]

been doing a boost leak tests for a while now but come to find out from a little searching on here I've only been doing it half right .question is is that how exactly do you know when your valves have no overlap so your leak test isnt being lost through your exhaust

 

[stomp]

could I just hook up the boost tester on the tb elbow pointing the tb and try it that way or would that be bad?