Cleaning up airbox

What is the best method to clean that white residue off the airbox?

 

I've had very good results with Macguires swirl X.
It has a very mild abrasive that has proven safe for all
finishes I've tried-paint.frame,alum,etc.
My air box was in pretty good shape but nothing really
helped with the white.
This stuff wont take it away altogether but will deff make it look
better.

 

You want it should look like this, right?



The one in the pic was as white as could be when I got the bike.

Then I discovered that I could scrape away the dead plastic with my fingernail; so I used the following method:

VERY very very carefully scrubbed with fine (grey) Scotchbrite JUST until the dead plastic residue was removed. Then I used a "scratch and swirl remover" product as mentioned above to rub out the surface; and in really gnarly spots I used Solvol (metal polish.) This was followed by a double treatment of Mothers Back-to-Black which did the trick.

On black plastic parts that have less dead plastic to be removed, all you need is the Back-to-Black.

http://www.mothers.com/02_products/06108_c.html

(One note about this stuff: I don't recommend using it on your seat, it makes it too shiny. Great for all those other black plastic bits like fenders and all the stuff under the seat.)