pretty good question i can tell you of what i know and there are probably a couple other guys that have more then i know as well but as far as i know these are some of the differences:
the 93 motor over the 91-92 has a mere 5-7hp more due to a slightly oversized throttle body
The suspension on the 93 is dropped back 3 inches i believe and is widend a tad as well to make it not as tail happy ( personal prefrence some like some dont)
The interior is identical other then the shifter is shorter in the 93
The tranny is more apt to have lsd on it but that is something that you can ghange no matter what.
other then that i dont know of any more. things that could go wrong other then the syncros likeing to give us all problems there is the fact that our car eats plugs and wires

there is probably more but that is all i know of good luck with the car and have fun autocrossing!