Any suggestions as to why when cold (below 15*f) at start up and first braking my pedal is super hard to push and truck does not want to stop. After the first stop or if I push-release and push again it softens up and acts normal. Only does it when really cold and at first braking.

 

There is a small check valve on a vacuum line between the break booster and the engine. Its probably needs to be replaced.

Maybe some one else can chime in on what the valve is called. Haha

 

That sounds right "check valve" or power booster check valve.