Hmm... P1399 isn't listed in Actron's database, either
(http://www.actron.com/code_lookup.php)

A good place to start would be fuel injector cleaner and fuel dryer (a
separate product - use both together). I'm thinking fuel because you don't
complain of misfires affecting your driving and an ignition system that new
isn't likely to be weak on all cylinders without failing completely by now.

If the injector cleaning doesn't help, the next step would be an ignition
tuneup. New as these parts are, one of them could be breaking down. If the
injector cleaner or fuel dryer does help, you might want to change to a
different gas station.

Mike