A4 Mileage + Audio Questions

[Byas U Nambisan <Byas_U_Nambisan@ccm.fm.intel.com>]

After seeing some postings showing really low mileages for A4s, I 
thought I should post mine. My A4 (manual) is about 7 months old with 
~6000miles on it.  It has averaged about 25mpg in mixed highway (70%) 
suburban (30%) driving.  The highway average has been around 27Mpg with 
best recorded mileage of 29.5mpg (over ~3gallons).

While installing my CD I noticed that the two rear speakers on my car 
are not identical to each other.  the one on the left has a metal cover 
over the magnet, while the one on the right was just a plastic cover. I 
suspected that it is to shield the speakers from the nearby CD (or amp).
Is my assumption right?

Byas
96 A4 Black
80 Fiat Spi 2000FI