I would try adjusting the idle screw , myself , were it me .

What does the tach show it is idling at ? Seem to remember our Sonic idles around 700 - 800 rpm ?

I have one of the little blue dongles that plugs into the OBDII port & Torque on my Android phone .

I may check to see what kind of real time data I can discover . Do you have Torque Pro ?

God bless
Wyr