Barnes & Noble, a literature super store with thousands of books and magazines. Among those magazines you'll find one going by the name "Import Tuner" and in the August 2001 edition of said magazine on page 14 you'll find some of the following quotes.
None of the body kits in the US have ever been through a wind tunnel.
Most of the spoilers designed for the aftermarket import scene are for show only and are not set up to provide the proper amount of downforce in the right areas.