I guess if Mitsubishi put them there, they must provide some benefit, but I had one fall out after putting my bumper back on and don't want to take it off again.

Anyone know what they do?

 

I imagine its part of the crash crush structure. Doest take much labor to pull the cover off, again, & install the foam (glue or tape them in)

Make us proud & install it

 

I hate removing and re-installing the bumper, but I'll do it again to make you proud...

 

I believe that the foam absorbs the vibration as well to prevent the bumper from rattling as well as making sure it sits properly.

 

Yeah the foam helps to keep the bumper centered and fit nicely with the front bumper beam. It also acts as a cushion to help those low speed impact in conjunction with that bumper beam.

If you still have the factory crash beam I'd reinstall the foam personally. And taking off the bumper is cake. Only annoying part is the clips if you have your undertray still on the car.