At idle, listen to the pulley side of the */C and listen for a rattle...If it'* rattling, then that'* a coupler. Easy fix though. If the guy will let you, bring a 15mm socket and breaker bar, relieve the belt tension on the */C belt, and turn the */C pulley back and forth a few times and check the play.....that'* the best way to check for a coupler.
For stock boost levels, prolly about 7 LBS maybe? And that'* with crackin' on the pedel as hard as you can.
I'm not too sure as my boost gauge didn't work until about 2 weeks ago lol.
Other than that stuff, I think you got it all pretty well covered....Make sure you get some pics to ***** off for us