So i changed a driver caliper yesterday and bleed the hole system. Got good pedal with truck off and nothing with it running. I'm thinking booster. Any other ideas? And i bleed all four wheels.

 

don't think it's ur booster. u had good pedal B4 u changed the caliper? why did u change caliper? it was stuck?

 

Pedal wasn't best in the world. Went to put brakes on it and found out that the drivers knuckle was wrong. It had a caliper and bracket and not just knuckle that bolted caliper bolted to. With the truck running you can hear air being sucked in when you press brake pedal. Doesn't make sound when truck is off. Also if I take the line off the booster I have a good pedal with truck running and block the vacuum line going to motor.