I replaced vac lines according to where they were on 96 DD51T and with posted diagrams. Accessory Idle up is fully engaged with no accessories turned on( screw is off seat with engine off- turn engine on and it pushes throttle way high)...checked idle up control and it is creating strong vac. Does this mean the control itself is toast? I plugged vac line at acc idle up pot and increased my base idle a little and truck seems to run fine, which leads me to wonder do I even need the acc idle up at all? Any advice would be appreciated.