-1.5 for the rear and -1 for the front should do the job. Depending on the track's spec and the drivers AWDs are not that great for track usage. It is very hard to overcome the lag if you are not a turbo car driving expert. If you have a 3.0i or anything that is more powerfull you have a very good chance to finish ahead of them.
To back up my above statement, I own a manual 2003 3.0 with stock everything. I have managed high 56's where the Evo Xs are faster than me by only 1 sec. I am pretty sure BBk and slick would be enough to catch them. I also own a Eagle Talon AWD with stroked and highly tuned 4G63 Evo engine. The car is just a pain in the ass to drive on track. Even though I have more than 400hp at 19psi, I could only managed a low 54 (the car has BBK, Coilovers, thicker sway bars etc etc..)
Wish you all the best for your fun day.