@3letterslong
Perhaps doing some non-power breathing drills could teach you better how to not breath with your neck (which sounds like may be the case), which in turn could help with the power breathing by generating better "breathing coordination." I too, have dealt with lots of neck tension, and the following has helped me a lot.
You don't really have to be in a specific position to feel this; I can get it to work sitting or laying on my back. It comes from PRI-inspired drills, as far as I can tell.
Take a breath in. Nothing special yet. When you exhale, exhale through a loosely open mouth, letting your jaw basically go limp. As you exhale, do it like you are trying to fog up a huge window or mirror. Exhale until all the air is out. If you do, you will find that your abs contract very well. Now,
when you inhale, inhale through your nose, but make it as quiet as you can. Even though the mouth is closed on the inhale, keep the jaw relaxed and tongue resting on the roof of the mouth.
I don't know what it is about the inhaling quietly, but in me it always produces the effect of ribcage expansion. I can feel my diaphragm contract and my belly expand, but
also my ribcage. Not my neck.
Tight jaw almost always equals a tight neck. I have developed the habit of relaxing my face and jaw as much as I can when training, and it makes a world of difference.
When I do a power breath,
to me, it feels like a
very short version of the exhale above. Abs, not neck. Personally, I find it takes a bit of practice to use the "tssa!" kind of sound withot also tensing the head and neck.