Even 20 seems low to me. But you may be idling slower thus the decrease. Both our bikes idle at 40 PSI sometimes drops to 35 PSI at about 1,000 RPM (if you can trust the stock tach) And hit 80 PSI as soon as the throttle is twisted. Maybe you guys have more miles and the pump is a little more worn than ours too.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!