Spot on, should go to 1.1 bar when overboosting, check it by flooring it from low down in 3rd, (boost is restricted in 1st and 2nd to preserve the transmision) However the standard engine and head gasket can be safely run to 1.4 bar, anything over that needs larger head bolts and different gasket.
Fist thing to check is the turbo pressure regulator located near the cooler. The pierburg valve could be broken or connected wrong. Do you hear a wissling sound when you floor it? Otherwise it could be the hose that is connected to the pipe between the air filter and inlet that is broken.
Check all hoses, those italian hoses with 10 years on their necks are a bit junky.
Hmm... if you only get 0.5-0.6 which is the "base" turbo pressure im quite convinced that it is the turbo pressure regulator that is broken or connected wrong. If you like me would get varying turbo pressure it could be the hoses or a broken turbo.
Tho two hoses from the Pierburg valve to the actuator and =ve pressure side of the turbo were on the wrong way round, the cra now makes 0.9 - 1.1 bar boost and makes me smile. How it should be. Great!!