I replaced a damaged front passenger fender on a 96 Legacy wagon I bought a couple years ago but I never replaced the crunched black plastic plenum that mounted inside the fender. Will that hurt anything? The only thing I've noticed is a deep "barooom" sound when putting my foot into it.   

Silencer and water seperator.

 

I've seen a stock legacy go thru a water crossing that swamped many toyotas and jeeps that same day...........short but deep crossing,the water seperator does work.

Won't hurt anything. Just don't try to ford any creeks that are more than fender height.

^^^ so made me think of oregon trail...

 

Flip the impreza over and ride across the Mississippi...