Not sure if this completely answers the question...
I only autocrossed my Mystique once... and it spun the inside tire like crazy. If you want to autocross get the trans. to Terry H. and have him install a Quaife LSD.
I'm also hooked on track days. If you have open track time at a large road course near by you'll be hooked too. Spending all day at an autocross doesn't seem like much fun after you've run a few full laps at speed on a serious road course. You really don't need an LSD depending on the track either (my opinion of course).
Finally, you may just do what I've done... spend all your hard earned money and buy a stinking race car. There's nothing like running in a good wheel to wheel/fender to fender regional club race with SCCA or NASA.
Good luck and have fun!