Tuning Minimum pressure

I have an fx wildcat mk3.25 cal
Power plenum
Huma transfer port and probe
I have tuned it for higher power settings With the regulator set at around 150 bar shooting 36g slugs between 920-950 fps .where I am confused I for the first time today was plinking targets and checking speeds on my chrono since the temperature drop we have had the past few days and realized my main air gauge was all the way down to 98-100 bar but my velocity wasn't suffering.i usually top the gun off when it gets to 150 bar .I'm lost ,can anyone give me some insight?