I noticed the same thing. We were on a trail in Anza Borrego and the floor was really hot. I've never felt a floor get so hot.
I later looked under the X and found that there were 2 catalytic coverters (I have a V6) right under the hump on both sides. I also noticed that the muffler at the end of the exhaust system had a blueish straw color to the metal. I'm guessing there are signs that the exhaust at the inlet of the muffler is at times 900 degrees.
Now I know the engineers that develope this stuff are pretty smart but I changed the muffler(Raven) to reduce back pressure and sure enough the heat dropped down. The exhaust has a very mild note.