What is the little circular light for, within the analog speedometer gauge? There is a circle for a light that I've never seen lit. It is on the right side of the analog speedometer gauge. Thoughts?

Sorry, edited my second question as I figured that out.

 

there is a trailer turn signal indicator in there, but its a circel with an arrow on either side of it.

 

I haven't noticed it in mine, but based on your description and what I can find in the iOS Cayenne manual it sounds like it's the "Upshift indicator". The manual says that it is only for manual transmissions and lights up to tell you to shift up a gear for fuel consumption savings when not in Sport mode.

Having not looked for it on my dash I would guess that it might be on all the cars but it doesn't do anything for most of us.