Try spraying some throttle body cleaner around the intake manifold near #6. If it changes the idle, you've got an intake manifold leak in that area. The unmetered air getting sucked in leans out the air/fuel mixture and can cause misfires as far as the PCM is concerned.
Hook that scanner back up, clear the codes, and have someone take it for a drive while you monitor the pending P codes to see if/how soon the P0306 pops right back as pending and how soon it becomes a hard code. The lean code will probably take longer to show up.
For the bank 2 lean code (same bank as "misfire" on 6), I think you need to solve the issue w #6 first since it may be that an intake manifold leak is setting a legitimate lean code, and there is no point in shotgunning parts unless you like having less money in your pocket.
The only other semi-educated guess would be a spent O2 sensor on that bank (Bank 2 Sensor 1).
But that does not explain the misfire, so hold off on that
