Hi ylwagon,If the CTS is truly working correctly, then an air leak or low fuel pressure are possibilities. But I disagree about the fuel filter. A dirty fuel filter acts similarly to a resistor in series with an electrical load: When supplying current to a very small light bulb, the resistor may be insignificant. But use a large bulb instead, the Voltage may be lowered significantly by the same resistor.
In the case of your starting issue, consider that the lowest demand for fuel flow is at cranking RPM, while the highest demand for fuel flow is at full-throttle, max RPM. So a filter clogged enough to prevent the engine from starting, would be too clogged for driving.
Does air leak and/or low fuel pressure affect only first time engine start in the cold morning? I am asking because my car works fine after having a hard start once in the morning.