I remember when I first moved over to OB in 2005...there was a diverse group of people who owned anything and everything. Most of the "original" group of IDI owners came in a series of waves in 2005 from thedieselstop.com due to changes in how that site was run. Over the next couple of years, the IDI section really flourished, while the people who owned other trucks (Dodges, PSD's, and even the occasional Chebby owner) drifted off...IIRC the PSD guys went to superdutydiesel.com but I really don't know where the others went.
Unfortunately, as they drifted away, the traffic on the boards other than the IDI section pretty much dried up...and it's a shame; I've always had a great level of admiration for the 12 valve 6BT and, like you, am trying to learn more about them...hopefully I'll own one someday
It'd be nice to see more traffic on the rest of the site, but I don't know how to lure people over...