I have not experienced those hoses specifically, but I believe one is a vacuum line which probably runs to that high-vacuum port you refer to. The other is an intake line. I'm not sure where it connects, but probably somewhere on the intake-side, upwind of the throttle-body. I believe the one connected to the high-side vacuum has a one-way diverter valve. If your engine is stalling, my guess is you have the hose routings reversed. Just a guess until I get up close and personal. I'll look at my setup tonight and let you know. Probably by then, though, some other guru on this site will have pegged your problem for you.
PS - That vacuum system helps remove moisture from the Opti internals, but for the life of me, I can not see how moisture can get inside of that sealed unit! I can see how the unsealed units sucked water however.