Brake pedal firmness issue

[Guanfy]

I'm having an issue where the pedal travel is a bit long when the brakes are cold. The pedal does get firm at the end of the travel and stop the truck, but there is quite a bit of travel until that happens. Once the brakes warm up, the pedal travel is much shorter and the brakes are much more responsive and even drag ever so slightly. I've adjusted the booster pushrod a bit which helped with the dragging once the brakes warmed up, but I still can't figure out why I don't get consistent pedal travel. I have 95-97 brakes in the front and mustang disc brakes in the back. The only thing I can think of is that I have air in the lines somewhere. To that end I bled all four brakes in the correct sequence (PR, DR, PF, DF) for a total of 10 pumps of the pedal on each corner. With the engine off the brake pedal firms up nicely and stays firm once the booster tank is empty. No visible leaks in the braking system that I can see and the fluid level in the master cylinder is not dropping. Could there still be air trapped in the RABS valve? Any suggestions on fixing this one would be great.