I thought all Mystique LS models had the V-6 engine standard (I know in '99 that was the case). Also, I have the original Mystique brochures from both 1998 and 1999, and neither one of them mentions anything about a "Sport" option for the Mystique.

-Mark- '99 Mystique LS, totally original (including the original water pump and the premium stereo)! Bought new in December 1998 for $21,000. 208,000 miles