It's worth getting a more accurate gauge because Torr (mmHg) is a barometric measurement rather than pressure; although it may not be much, it's affected by temperature. Bar, atmospheres, pascals, and PSI are valid pressure measurements.... plus if you run over the factory boost level you'll go off the top of that gauge.
It's a bit of a pain to set up a boost controller like this; I made and adjustment, took it for a drive (usually involving the A55 so I could open it up)... then opened the bonnet, made an adjustment, took it for a drive... until I was happy it was making the boost level I was after (1bar). - You could also do it on a rolling road, but I don't think it's worth the money seeing as you were only on one a couple of days ago.
700mmHg (the highest value on the standard Pulsar boost gauge) is about 0.9bar at STP, so that gives you a little headroom to play with.