Hi Dimi,
14PSI seems to be standard on the AR-X so it is safe for you to run that. Our standard turbo's are probably starting to limits of longevity at 16PSI. If I was you I would stay away from manual bleed valve and go with something like HDI-SBC-D-EVOLUTION (http://www.hybrid-power.com/index.php) or simular......my reasoning behind this is that they will create and hold boost a lot better than a manual one.
Pretty sure the boost cut is 21PSI.....I know when we were pushing the Haltech I put on, we hit it at 21PSI but I have heard of someone else running more PSI with a different piggyback.
By the way if the turbo lets go...which it will....it's a bitch of a job...lol!