[Carbuff2]

I would double-verify grounding and connections because of the flicker. The large battery leads can corrode inside the isulation when the car sits for long periods... Twist the terminals without loosening, if you can turn them your battery may need terminal shim (only a couple bux at autoparts stores)

One thing that has happened on our '06 is that it will occasionally not start after warm running. Turn the ignition OFF, count to10-Missisippi, and it would always reset and start fine.

P1457 could just be an old gas cap, but a 'small EVAP' leak will not affect running, in my experience.

 

[Carbuff2]

Idle: If the mechanic didn't do it, clean the throttle body. Do not spray (that could damage the TPS), just wipe the throttle bore and butterfly flap clean. THEN do the Idle Learn Procedure. (SEARCH or Google)

Grounds: Follow the big wires back from the battery and make sure the body & engine sides are clean and not corroded (especially if you live in areas with road salt).

Before you go crazy tracing that stuff, verify that your battery and alternator are working correctly. (Have a shop LOAD TEST them) A good auto electric shop can test for bad diodes in the alternator that can affect the consistency of its output.