[RICK LAKE]

Voltair Check a couple of things
If you let the motor idle for too long it is possible you carboned up an o2 sensor and tne motor thinks to try and lean out that side of the motor. The swapping of o2 sensors will give you help to see if it's that side of the FI side of just an O2 sensor.
The other things to check are your fuel pressure at idle and fuel filter
Is the gas new in the tank or has it been sitting for a while?
The final thing is it's possible you have a leaned out cylinder with a poor spray pattern from the injector. You didn't say what the LSA is on this camshaft. Try running some injection cleaner throughs the rails.
See if you can find a dealership that does B&G services. This work pretty good for cleaning injectors in the car. Rick L.