Burning coolant

[Rawze]

most likely a slightly leaky injector cup if ya ask me.

only way to know for sure is to drop the pan and let it sit all weekend with 20 psi on it... turn it by hand and listen for a gurgle from a cylinder on a compression stroke.

If ya can't find it like that, then run it.. there is nothing you can do about it. Might want to consider converting it to a zero pressure system... that is what I did with mine when I found out it was seeping slight amounts of coolant at 270k~ish miles. After converting it to zero pressure, It made it to 980k before I finally got around to inframing it and found out it was cylinder #6 injector cup.
zero-pressure conversion http://rawze.com/forums/showthread.php?t...9#pid13369

my truck now has 1.4 million miles on it... it is still a zero pressure system, I use regular red ELC coolant.