Found the problem.. ed you were right, it was a leak. turns out 1) there was a hole in the in one of my vacuum lines, and 2) the hose connecting my BOV flange to the BOV had come undone and popped off. that explains the lack of a "kssh" sound that i noticed on the way home today. moral of the story: don't try and troubleshoot your car at 2am with a flashlight.