My thought on the plugged coolant passages was an additional effort to cure the external coolant leak so many 6.9's would experience (resulting in numerous head gasket changes over the years), but the emissions idea is plausible. It's also the reason in my opinion that so many 7.3's have overheating issues.
Thanks for approving of the write up in the article. Jim did a great job, and I know every truck there was worthy of coverage in my opinion, but we all know they can't do an all IDI issue. My hope is that everyone gets a turn eventually. I've waited 30 years for my turn. It seems only fair to me that I got my limelight finally. I'm thankful that so many other trucks got at least a mention. I'm hoping that some of you will write the magazine and compliment them on this coverage. Doing so may encourage them to do this kind of thing more often, giving more of you a chance. I've subscribed for the year, so I can watch the readers comments if nothing else.