So I figure that it is either the STC fitting, or the rail-to-head tube o-rings. I pulled the RH valve cover off the other night and replaced the o-rings, but they looked fine, I just wanted a little insurance in case one was thinking of taking a dump anytime soon.
Tomorrow I am going to do the other side and get down to the HPOP to replace the STC fitting with the solid screw on piece. I got the STC replacement kit and a TON of gaskets for everything I am dismantling (including all the gaskets to do an EGR delete) from my dealer for $120. I also got one of their diesel techs to print out the latest TSB on the STC replacement for me, so I have the good instructions and torque specs for everything. Hopefully I can have this resolved by tomorrow.