Thank you for the replies everyone. I know the engines will flame out, but this also means they've reached some sort of below minimum point but what I seek to know through the GUI is how close I am to that point. At some point the engine is only 50% effective because of lack of air, but how does one know that from the UI?
Regex, thank you for the F12 hotkey hint. I loaded things up and took a look, it displays information about the air density but no per-part information like an intake's satisfaction.
Small followup on the F12 stuff, air density is certainly useful but air speed would also affect intake air and the different intakes have different levels of effectiveness at different speeds... so there are lots of complicated factors and I'm just trying to figure out if my engines are underfed through a gauge on screen of some sort.