[habbyguy]

FWIW, I was installing wood floor in my classic RV (a 1978 GMC) and carpet in the cockpit (above the engine compartment, because it's a front wheel drive coach). I ended up using the underlayment that I'd bought for installing the wood floor up front over the engine compartment. I put down two layers, using spray (headliner) adhesive, and it worked like a champ. Cheap, and a HUGE difference in noise coming up from my mighty V8 throbbing away a few feet from my rump. The stuff I used was essentially 3mm neoprene (think wetsuit), and not much sound gets through that.

I bring that up because I'm thinking of using the same stuff under my MDX front carpet, primarily to see if it will reduce the amount of torque converter whine getting into the cockpit. Assuming that the noise is coupling to the body acoustically, it should help quite a bit to put a layer of underlayment between the firewall and the cockpit. Couldn't hurt, and will also improve the insulation qualities.

FWIW, I also used the stuff because I had a bunch of it left over from doing wood floors in my house, so it was "free" (as was the wood floor in the RV). Even so, I'd buy more to do the same thing again, if only because I'm too cheap to buy Dynamat. ($157 for 36 square feet vs. $40 for 100 square feet of what looks very much like the stuff I used). https://www.houzz.com/product/66961124-100-sq-ft-underlayment-3-mm-eva-contemporary-flooring

 

[habbyguy]

The sunroof drain exits on that side where your leak is. The drain is plugged somewhere - you can test the system by pouring some water in the front left corner of the (open) sunroof channel, and seeing if it leaves the area. If it does, the plugged part is lower down.

 

[habbyguy]

There could be a leak in the hose to the drain, which could put a considerable amount of water onto the floor in that area. Here's a diagram of the routing...

It would be worth a look at the cables / hoses / etc. that go through the driver's side firewall. If one of them has a seriously damaged gasket, water that gets into the engine compartment could find its way through the firewall to the carpet, particularly on a cable / hose that leads down toward the firewall.

Also look for a gap in the sealant on the left side of your windshield - water getting into the pillar there will also run down to the same area.