With all this discussion on IAT #2's purpose, the only time I've ever remembered it being of any significance, was back when 06E17 was released. Shortly after, there were numerous owner complaints of driveability issues relating to bogging. What was found, was the EGR valve cycling quite erratically, including one vehicle that had come back for three visits before I could fix (back when I was "green" to fixing diesels, which I could still argue that I AM still "green"). Sure enough, cleaning off IAT #2 fixed the issue permanently. I vaguely recall a drastic increase the IAT #2 response to EGR valve being commanded open, as I was monitoring the PIDs. Just my