What is this part?
 

I just gave the trunk of my '99 protege a thorough cleaning after transporting some plants, and found this loose part. It looks like some kind of plug. At first I thought it had something to do with the spare tire, but I don't see where it would go. Any ideas? :confused:

I guess a reference scale would have been helpful.., The round "cap" is about 3" by 4", and the "spike" is about 5 1/2".

Another Update - Just noticed a part number on it:

K2443
BCID68838

Attachment 3928Attachment 3929

It has something to do with the air scoop for the brakes, front passanger side:
Air scoop for the brakes [Archive] - MN Mazda Forums