My gauge runs just a smidge above a bar. I fitted mine on the hose that runs from gate to fuel pump. You'll never see negative pressure as its not a dump valve and they run at a bar because thats what they run at,no fancy valves getting rid of excess boost. It you nedd more you can shorten the acuator arm,but you'll need to cut some of the thread off to make a real difference.
On a side note a no cat,with straight through middle exhaust does seem to help the turbo spool up quicker.