Did a pressure test today to make sure all my hose clamps were tight. It identified that the throttle body heater is leaking yet again, so that's cool, but it also showed a stream of coolant coming from somewhere on the back of the motor. Any ideas?

 

This is a tough location. Anti-freeze can run down from the valley pan area, if lower intake is leaking, and look like a head gasket...or it could be the head gasket. Get in there with a mirror and see if you can determine the area of origin.

 

I can't tell anything specific from your pics, but a very common headgasket failure point is the rear of either head. That's where the coolant passages run from the block to the heads, and the headgaskets are very narrow there (maybe 1/8"). Bummer.

 

That sucks if it’s head gaskets.
Just out of curiosity. What is your coolant temperature??

 

188.6 on the freeway and under load. 183.2 downhill on the freeway. 194 at a stop light.

 

clean off the areas really good and get in there and check with a mirror as @The Deputy mentioned.

 

wow those are awesome. Good luck with the fix. Hopefully it’s something simple

 

I have a similar leak. Very small with droplets under the cross member that is near where the front prop shaft attaches to the front diff. Not a bad leak, my engine temps are fine. Let us know if you find where the coolant is coming from.

 

Check with a flashlight etc from the front as well behind the alternator and ac compressor - looking down at the valley pan.
On a different thread I spoke about my leak but it was the front of the valley pan.
Long story short - ALL of the valley pan bolts were loose. - apparently a known issue.......
I only removed the intake plenum - alternator, ac compressor and its bracket and fuel rail.
Some say you can get to those bolts with a 1/4 drive around the fuel rail but at that point it was easy enough to just remove it and get a proper sized socket down there and use my torque wrench correctly.
I pulled all of the bolts, IN ORDER, one at a time, and added blue loctite, then reinstalled IN ORDER and torqued in two stages since my torque wrench doesnt go below 20ft lbs.
I've since put several hundreds miles on it with no leaking at all., Never had temp issues, same as you........

 

Closing out the thread - was a leaking head gasket. The water jacket at the rear of the right-hand gasket was the cause. New head gasket, no leaks!