Today car is running great! Check engine light is still on but it hasn't been reset. Drives with no miss, idling smoothly with no service ESC/ traction.... Kinda weird, it has days it runs good and days it misses bad and wants to stall out...

 

If you want to turn off the ECL, you can disconnect the NEGATIVE battery post under the trunk's floor, (next to the spare tire) for 5 mins, then reconnect it. You just have to be careful not to short out the negative side of the battery to the positive side.

That is sorta good news, that it is running well, but whatever is causing the problem hasn't gone away. The computer is constantly analyzing things, and if it detects certain errors over a period of time/and or distance, it will light up that CEL.

Oh, check the invoice/workorder from the mechanic that changed the plugs - these cars get real fussy if using anything other than Delco Iridium plugs sparkplugs, and can generate misfires as well.