ok. First of all there are no 'specificly' made 2001+ kits out on the market as of now except for the Xenon kit (sedan) The other lip kits (Kaminari and Wings West) do not fit perfectly because of the front bumper, but the sides and rear valence fit.

Full bumper replacement body kits do not usually fit perfectly and have to be modified a little to be made to fit. They dont fit perfectly cause they are not always carefully made and sometimes poor quality.... thats basically it.

The only real way to find out if it fits or not is to try on your own car I was able to fit a full bumper replacement body kit on my car (2001 sedan) w/o too much trouble, but there were modifications made to the kit, to make it fit.