You're right ender, at speeds it could even be within a few degrees of ambient.
However, I'd be floored if I saw a 1 psi drop through an intake... I've never seen that.
I've hooked up vac gauges before, and If I saw even 1 HG INCH at WOT with the stock intake, I'd be pissed...
There should be no discernable difference in pressure with a proprly designed intake.