1) Google search says poor fuel economy may occur with potential stalling. Constantly too rich fuel mixture could foul sparkplugs and oxygen sensors. It sounds like it's not critical but don't wait too long.
2) Manifold Absolute Pressure sensor signal low.
3) Lots of potential causes. Connector on sensor is loose, sensor itself is bad, wiring to sensor is bad, engine computer is bad, leak in the intake system.