Coolant leak behind psg head. Valley is dry!

[bondsman]

I was going to install my stereo today so I parked it on the concrete (it is usually parked in gravel. Started running wires and noticed red ELC on the ground. It is under the passenger side. Looking up from underneath, the rear exhaust manifold was wet at the back. After carefully cutting some of the plastic inner fenderwell so I could see towards the rear of the engine, it is coming from behind the head. The degas bottle is low too.
Now, here is where it gets tricky.... EGR deleted...
Checked the valley-dry.
Checked under the intake manifold where the EGR delete connects and the silicone hose where it connects to the oil cooler - both dry.
Head studs and black onyx gaskets installed 6k ago.
Heater hoses-dry.
Heater valve - dry.

Is there a coolant drain plug on the heads? I don't remember from when I pulled my heads.

Where could this coolant be coming from??

[NYC F-350]

Sounds like you have already checked the usual spots. You might have to go get some of that dye and pour it into the coolant to find your leak.

[bondsman]

Found it.... Turns out it was the tee for the coolant filter. It was seeping out onto the harness below it and running down the valve cover gasket. Scared the hell out of me. Time to get some hose and a brass tee fitting now..