2005 5.3 Tahoe running rough/stalling only when hot

[1919]

So I finally got back around to fooling with this thing. I've been considering the head gasket for a while now, and so investigated that and discovered that I have bubbles coming up in the water tank. After this I done a compression test.
I have 2 cylinders at 170 and one at 165 on the right bank. Couldn't get the adapter into #8.
The left bank is 175 on #5 and #7. #1 and #3 are both 158 psi. This makes me wonder about a gasket issue around these 2 lower cylinders, but they're also not terribly low. Anybody have any thoughts or recommendations on this?

 

[Fless]

You may want to try a test like this: Coolant Test for Exhaust Gasses

 

[1919]

You may want to try a test like this: Coolant Test for Exhaust Gasses

I actually have a carbon monoxide detector that I could hold over the water tank and see if it alerts. If it does I'd think that's pretty definitive. Thanks very much for the idea!