Intake hose failure is common. The hose will open during boost and allow air measured by the AMM to blow out instead of into the intake manifold. Usually happens on bottom side where you cannot see it. If you look carefully when it happens, you may see a light trail of black smoke behind you. Sometimes engine twist will cause the tear to open more at some times than others, making it seem intermittant. It wasn't until I took all the hoses off and found a little blister on the inside that I realized there was a cut on the outside too, just where the clamp holds it. All hoses after the turbo are suspect.