More than anything I just wanted to put some information out there so others that beat their head against the wall trying to figure this out might find this thread.
A few months ago I swapped out engines, as mine shot craps. With that said...thing would run great, but idled a bit high. After a few minutes if it was left at idle, lightening bolt light would come on....sputtered and stopped running. If I was driving normally...It would never happen. Only when left at idle for a few minutes.
After a few times of this...the ECM finally threw out some codes.
P0507 and P2173
Then the research began. Both, from internet reading...suggested there was a vaccuum leak somewhere. Looked and looked...couldn't find it. Rubber lines were fine...so it continued.
Yesterday, I heard a hissing. When I tracked it down, I understood why I couldn't find it. It was the metal EGR tube. It had a very small crack in it...beneath the heat shield cover. I only found it because I was looking at it while the engine was still cold. I could stick my hand on it. Every other time, the engine had been running and that tube gets hot...not a chance I had touched it before.
Soo...long story short. I bit of metal heat tape and the codes went away, idle is back down to normal and life is good. Short term fix till I can find another tube. Hope this helps someone down the road avoid the headbutting of the nearest wall. Cheers mates !