evo mr fu.
if your gauge is at 0 when the car is off then chances are the gauge is fine. if it were off (in your case since the gauge only goes to 1 bar at full boost it would be "reading" vaccum when off)
sound to me that you have a leak somewhere cause you arent reading as much vaccum or as much boost as you should be when the cars on.
however, that doesnt mean the leak is in the line to the gauge.

 

??????

 

what other places can I check for a leak?

what do you mean by. " in your case since the gauge only goes to 1 bar at full boost it would be "reading" vaccum when off" How does it read vaccum when the engine is off? when the engine is off its just at 0

 

he meant when the engine is off that the neddle will be under the 0 into the vacumm section

 

check ic pipes they tend the loosen up by the clamps check blow off vavle

 

why would the needle be under 0 if the engine is off?