If the resonance flaps are the problem the intake manifold needs to be replaced( the flaps/valves are inside the manifold and can't be serviced ). I doubt that's the problem though. Either a bad fuel pump or the engine management ( ME-SFI 2.8 ) control module is no good. Another possibility is moisture/corrosion in the connector for the Crankshaft Position Sensor. There have been service bulletins concerning this but I have yet to see it. Fuel pump or ECU. Keep me posted.