The engine is a V6 OHV. I am having an intermitted loss of power problem. I have cods P1131 fuel air metering and P0171 System Tool Lean (Bank1). The trouble shooting indicates a dirty mass flow sensor, or loss of vacuum downstream of the sensor, as I side the problem is intermitted can a vacuum problem be intermitted? It has been suggested to me that it could be an intake manifold gasket. Is there a common problem with this engine that results in the above summations?