Just a heads up that the aftermarket mats don't cover the exposed area either. I removed the styrofoam wedge and had that same gap. I then installed the diamond mats (which I love - easy to keep clean and look great) but they also had a gap. I was able to find matching material on Amazon and cover the exposed area.
I should point out that there is a bracket that supports the dash in that area that makes it a bit tricky to cover. What I did is took a piece of ABS acrylic (you can use fiberboard or any other thin but flexible material) and cut a rectangle about 12 inches wide and 8 inches high. I then wrapped one side using spray adhesive to attach the material to the rectangle. I then drilled a small hole that lined up with a bolt on the aforementioned dash bracket, and attached the now upholstered plate in place. The bolt is towards the bottom of the upholstered rectangle and is covered by the floor mats.
I have circled the area in the picture below so you can see where I installed it as well as the size of the gap it covers. The material I purchased doesn't match exactly, but seeing you have to be down on your knees to see it, it doesn't show unless you point it out. You can do the same with carpet material. You can get black automotive carpet by the yard on Amazon. You will only need to order 1 yard as you won't use even a fourth of it.
One last bit of advice. The diamond quilt mats are priced from around a hundred bucks to just over two hundred. The less expensive mats do not cover the center tunnel between the seats. That is the area highlighted in the picture below:
