Hey fellas, have been searching the net quite a bit and just wanted to ask for some advice and document my problem.

My 06 GP (v6) recently developed a distilled vinegar like smell that comes from the vents. It is very noticeable upon first starting the car and turning on the vents. After driving for ~5 min it is either less noticeable OR maybe my nose just got used to it. Happens with fan only, cold AC & heat. Possibly unrelated but I also notice fogging on the lower windshield at night when car is parked & a slosh noise behind dash (I realize this may be coolant related, detailed below.

What i've tried so far:

I found a suggestion to remove the coolant overflow tank and reach in remove the elbow and prod around in the drainage hole. Using a small center punch I inserted it all the way easily, when removed it was dry. I then cut about 8-12" of string trimmer line and fished it into the hole easily, spun it some, was also dry upon removal.

That didn't seem to do anything so I assume either I didn't go deep enough or the line isnt the problem? Its 65F in Florida and not too humid, not sure how long i'd need to run the AC to make water drainage from the elbow to verify it's not clogged.

Next I followed advice from an old forum post: I peeled back the passenger carpet, the carpet & padding looks like it has never gotten wet before. I was looking for a hose connected to the black box under the glove box, supposedly I can remove this hose and then insert a wire into the black box nipple to check for any clogs? I only seen a very small diameter (less than a pencil) hard black plastic tube, im assuming that isn't the right one.

Aside from this, the only other issue that is occuring is a water slosh coming from dash area. I read this is probably due to low coolant/air in heater core and likely unrelated to the vinegar smell? Some posts say this slosh is only due to coolant while other posts say that it can also be due to a clog in the condensation system. Note: the heater works extremely well so I think that would rule out air trapped in heater core?

Lastly, i'm aware of the windshield cowel mod and will be ordering the GM PN 15794785 to complete it. My cowl is in pretty rough shape as well, most of the foam edging is disintegrated. Not sure if the cowel/blower would be the culprit but thought i'd mention it.

Going to keep searching, will update meanwhile if I make any progress.
Thanks for your time fellas!