Odd noise from dash when accelerating or turning left

This literally just started happening today as my wife turned into our neighborhood. 2014 Acadia Denali with 249k. It is coming from the passenger side and sounds fluid related...almost like a fine stream spraying out (almost like steam) or into a fan. My instant thought is heater core and water is being chopped by the blower fan. It only happens with the fan on and does it regardless of A/C on or not. I thought with accelerating it's the increased water pressure that is helping cause it, but it doesn't do it when in neutral and revving engine (odd). Also not sure why only left except that maybe the heater is towards the left of blower and a left turn makes water flow right (and therefore into it?!).

Possible holes in my theory- I don't smell ANYTHING. I was a mechanic for several years and replaced water pump / hoses on this vehicle. Warm coolant usually has a smell (especially in the interior). I can't find signs of water leaks...under vehicle or inside...no wet carpet, etc. I removed glovebox & cabin filter and it doesn't help narrow it down.

It's possible this is just a SUPER small leak, but need some insight. Where is core in this vehicle? Appears hoses enter at driver's side, so suspect it's there. Any other ideas?!?