Sorry no picture, but when I removed the IACV valve assy to clean, I see through the opening that there's a hole/indent on the bottom of what I think is the main air flow chamber. What is that? Is it the EGR tube inlet?

As far as I can tell, that hole/indent in my car is clogged. Is there a way to clean it from there? Or is there a solvent/cleaner I can safely use?

 

You need to clean the carbon out of there. This is where the exhaust gas gets introduced into the plenum. Napa makes a product called Macs throttle body and choke cleaner but any throttle body choke/carb spray should be fine. Its tough spot to clean.

 

Maybe that's why my car has been dying under braking. That area in mention is darned clogged. Anybody has any creative ideas that they've used to clean this inlet?

 

If that hole/passage is clogged, then your egr tube is most likely clogged as well. You need to remove the egr tube to clean it.