why is bov hitting under vacuum?

[flyneagle]

ok, my friend has a turbo accord with a t25 setup w/1g bov. His bov hits at like 5psi vacuum or even 0 psi?....its only when he hits the gas real hard....it goes off under boost also...but why would it go off when its still in vacuum???he didnt even build boost yet????....let me know... thanks guys

 

[1993eclipseGS]

It goes off because there is still air in the piping to discharge, Even when he doesn't hit boost.