Have you noticed this under load ? The 34 like the 33 is limited to .5 bar until you hit 3500rpm. Goto fourth and kick back to third, then double check that it hits .7 bar. Generally speaking the 34 factory boost gauge is fairly accurate, when it does begin to play up you get an all or nothing reading. I've had a autometer boost gauge, blitz electronic boost gauge, and the factory boost gauge and they all are pretty accurate. Stan (satanic) also runs three boost gauges and finds the factory one pretty close to the mark on the 34's.
Also do a hard ecu reset in case it's your AFM playing up.