My 2010 E350 has a metal plate attached to the floor behind the accelerator. It is about same length as accelerator and stands about 2-3" tall. Secured by two big bolts and appears to have been installed after the carpet.
Anyone know what it is for?
Would send picture, but do not have capability.
The two bolts are exposed, rather than being covered which seems unusual for an M-B.

 

It's for putting the pedal to the metal. It simply wouldn't do to put the pedal to the carpet.

My 2010 E550 has more of a hard plastic box behind the pedal secured by exposed bolts.