Right - seems this is the best we have at the moment in terms of numbers:
http://www.ft86club.com/forums/showthread.php?t=47937
The raw numbers for basic kits don't seem to be that impressive (thing low 14s to high 13s) but worth noting that it seems that our cars suffer from a few peculiarities which affect 1/4 mile times, most notably off the line traction and a shift into 5th before the timing lights.
So, even taking the #s with a grain of salt, it seems that a basic kit will get you a definite (if moderate) benefit in terms of acceleration.