Well, I keep performing COLA Brake Test every time I fire up. After pop off, I depress service brake, turn off motor, release Spring Brake and watch the guage, it drops way more than 3lbs. A couple secs later I hear air expelling, like I'm lifting my foot but I'm not, thats what I mean by the "pedal drop". Applying further just increases the rate of air psi loss. Maybe leak at air relay, thats the valve assembly behind pedal assembly, on exterior firewall in front cap.