You're on track. More than likely this is a false lean condition; meaning either unmetered air is entering the intake manifold and ultimately the combustion chambers, or the MAF sensor is not calculating the volume of air entering the engine, correctly. Inspect the mass air flow sensor for correct values at idle and 2500 rpms and then check for cracked/brittle or disconnected vacuum hoses, and even possibly, defective intake manifold gasket(s).
Inspect fuel trim at both idle and while cruising. If short term fuel trim is high during both conditions, suspect a vacuum leak behind or after the throttle plate.
It will not hurt to ensure your G35's air fuel ratio sensors are functioning properly either. To check the operating condition of your Infiniti's fuel ratio sensors we recommend conducting a fuel enrichment test using propane. Check that fuel ratio sensor signal voltage switches between .02 when rich and .09 when lean (this is the opposite of the values to check for when testing a regular oxygen sensor) as propane is added and removed. Take extra caution when using propane as it is extremely flammable.
