I will check TSB" technical Service Bullitns" when I get to work in the morning but ...... my guess is a chunk of carbon is holding the valve open since it fails closed. I would start by taking the valve off and cleaning it out. That 1" pipe goes down to the exhaust pipe behind the motor if I remember..... be carefull when you take that nut off the EGR valve so you dont twist the pipe and break it down below..... THAT will be a fun job
Kevin
Kevin