Max on standard turbo's is normally 1 bar, although some poeple risk 1.1-1.2 on splash boost if they have a boost controller. Not recommedned to be above 1 full time as the cermaic blabes in the turbos do have tendancy to shatter if run 1.1 and above.
If you're looking to go above 1 Bar you're ging to have to upgrade your turbos, which will not be cheap - like any skyline tuning ;-)
You won't hear it I can assure you. It's not the typical pinking you may have heard with other cars. Your description of the symptoms you are experiencing almost certainly describes the actions of the knock sensor. I know people may disagree with this but I have been told by those who know that the stock ecu will not properly fuel the car running at 1.0 bar. If you are running near to 1.0 bar then you may be running lean and getting some det. You need to take it to a Skyline tuner and get it checked out or you may regret it when you pop a piston or spark plug. All IMHO of course!
BTW, who said bleed valves aren't reliable, not me. What's that got to do with measuring the boost properly anyway?