Even though this vehicle has a throttle body this throttle body is used for air flow into the engine
and this engine actually has a separate injector for each cylinder.These injectors are located under the upper plastic intake.The intake has to be removed in order to replace a faulty injector.
It sounds like you have covered everything else here that could be at fault and the problem is still present so the fuel injector sounds like the most likely component for the Number 1 cylinder.I have seen these restrict and stick closed causing this exact fault here.
To test this a fuel pressure test gage is needed as well as a scan tool to pulse the injector,each injector would need pulsed and the fuel pressure drop on the pressure gage observed for each injector as the pressure should drop some when each one is pulsed.
If the #1 injector doesn't drop any pressure at all or if it drops any different then 1.5 to 2 pounds in difference then the rest of the injectors then it is faulty and needs replaced.
Any shop or dealer would have the pressure test gage as well as the scan tool to pulse each injector.
The replacement is usually about $100 for the injector and about $30 for the upper intake gasket set and around 2 to 2.5 hours labor to have replaced.
The injectors are very common on these engines as well as GM's 5.0 and 5.7 liter engines as they all use the same injector design.
Let me know if you need anything else,click accept if you feel satisfied with your answer as this is how I get credited for my time,Thanks Pete!