No power, cannot go over 50 mph, idles rough

Car gets up to around 40 mph just fine but then it goes to heck. Getting to 50 mph is a job. Down hill on the highway the car will slowly gain speed to cruise at 75 mph on down grades and flat lands but the minute any kind of incline is attempted the car falls flat on its face, rapidly going down to 3000 rpm and 35-40 mph for your uphill speed. The codes that popped were for a mis on cylinder 2 and mass air flow output voltage low. Unplugging the mass sensor did change my speeds by a little, letting me go faster on my uphill climb but only by a couple mph. I am also hearing a loud hiss sound on acceleration, almost like a turbo whine, I realize this is probably a vac leak that I need to track down. Thought I would ask for ideas before throwing money at parts. Thanks in advance.