Girlfriend just picked up a 2004 GS. On both doors there are small arc shaped cutouts about 3-4 inches long close to the edge of door near bottom. You can see the insulation through these openings. Looks like something was in these cutouts and was removed. Any ideas? Sorry no pics.

 

Those are reflectors. I just purchased a 2004 GS and noticed the same thing. I went to a Mitsubhishi Parts Dealer and he looked up the price. Very strange, one reflector cost $18 the other cost was $28. I figured I'll look for them elsewhere.