I have read and read and read the posts on the forum for info on this, but I have not encountered anything quite as un-diagnosable as this. Here's my situation:

-For a while, water has been pooling up in the backseat passenger floor of my 300cdt. Common symptom, right? I figured it was the window seals--the easy fix-- and went for that. No results. (I read in some post someone said it takes a few days for the rubber to conform to the window, but I don't think I'm lucky enough that it's that, although I just had them replaced 6 or so days ago).

-This failing, I tested further by putting a hose on the passenger side of my front windshield and observing where the water entered up in the front footwell. It was coming through in the seam where the bottom of the floor (the floor being a plastic hardcoat covering that flaky stuff I guess for sound-deadening and then the steel plate underneath) meets the right side panel of the footwell (as you're sitting in it).

It seemed straightforward enough, so I sealed the area with silicone sealant. I also sealed the hood pocket area behind the drain spots preventatively since it had a little rust (hopefully not a bad idea, but probably was since it sealed rust in ). I was in a water-stopping frenzy.

-Now when I test with the hose prior to these repairs, water still comes in, but instead of coming through the crack before, it comes through various other cracks in the plastic hardcoat in the bottom of the footwell like little f*#$ing springs.
This means that water must be somehow entering the space between the firewall and the plastic hardcoat, quickly soaking through and past the black sound-deadening stuff, and then welling up wherever it can find a place to get out.

Sure I could just seal all the cracks, but that would be a kind of retarded way to do it since there would then just be water sitting on the metal panel beneath, rusting it out.

The only solution I can think of is to crack the plastic hardcoat open all over the passenger footwell, scrape out the sound-deadening stuff, and search all over the metal panel for a hole where it is coming in. I'm afraid though that if I do that I won't find one and will have destroyed the footwell for nothing.

Could it be the seals have not adjusted yet? How could water be coming in this mysterious in-between space? Furthermore, how could rainwater, simulated or otherwise, even find its way in there? My suspicion is that it's coming through the area around or behind the hood pocket, although I sealed that.....

Please help me on this, I can post pictures later if needed. I'm on my last nerve with this water deal. I can take all the mechanical repairs associated with a 21 year-old car, but fixing rust and searching fruitlessly for a stupid little leak is infuriating. I was so happy thinking I had fixed this problem, and now I feel like getting a crap asian import just out of sheer desperation.