Yes, it's perhaps a problem with the trigger arm: this arm push on a valve rod which permits admission of vacuum in the bellow. The (57) FSM says "if pedal pressure releases slowly, adjust by rotating adjsutement screw (of the trigger arm) in counter-clockwise direction". If time delay, make a clockwise adjustement. In every case adjsutement must be limited to + or - 90 °. Note that in the canadian '57 FSM ther's a pic of a tool for this adjustement: like a clear plastic with 2 circles. I've tried to make it but i haven't very well understand the explanations... I think you'll not take much risk in trying the adjustement.. -- Philippe COURANT (Pau, France)- Webmaster des sites ACCF et C-I-F Imperial 1957 Crown convertible Buick 1958 Roadmaster sedan HT - American Car Club de France (ACCF) : http://www.accf.com - Chrysler Imperial France (C-I-F) : http://www.ifrance.com/c-i-f - Cadillac " Standard of Excellence " : http://www.ifrance.com/accf-cad - SportsCars : http://www.ifrance.com/accf-sprtcar