Theres no chance that it is coming in through an intake bolt? I had this happen, and I had even sealed the threads...or so I thought. I actually had puddles of coolant in the lifter valley. My heads are milled also, and I had to go without gaskets at both ends, just RTV. Also, could one intake bolt be too short to properly thread in deep enough maybe?...yep, I did that also. If there was a way to screw up a Mopar engine....I did it :(