The other day, I swear I hit 9.8 lbs of boost in the GS. Since the guage is digital, it'* easy to read the concise measurement. For some reason, I just don't think that'* possible in my 100% stock setup. Who knows - maybe the guage isn't calibrated right.
What was the temperature outside? Cold I bet. Denser air. You'll see less boost on a hot, humid day. Typical boost on a stock S2 should be in the 7.5-8 range IIRC. Yours seems a bit high even for cold weather.