You don't want it moving off the bottom of gauge, let along getting any where near half, your turbo is water cooled so you don't want to go on boost at all.
Better safe than sorry so you may as well NOT drive it, if it was your idler or tensioner bearing it will make the noise on start up and when idling, it will make a screeching sound that has a clear rotation sound, if its a turbo gasket it won't have that rotating type sound.