Here is a little tweaked setup for the fox. (I hope I'm posting the correct one)
http://rapidshare.de/files/11359263/FORMULA_XR_fe3_mod.set.html
I made it a bit less understeery on corner entry, and a bit less oversteery for exits.
Also try what espn suggested, make the suspension a bit softer, that will make it go through chicanes a bit smoother, and you'll get less tire wear. I also fooled around with the wing, but I unchanged that later. First I increased both front and rear wing by 2 degrees, car was much more stable, but was suffering on the straights. Then I decreased back the wings by 1 degree, was quite ok, but I somehow was running slower.
For the chicane, the 1st one that is, I lift of a tiny tiny bit, just let of the throttle 50%, and smash it tight again. This before entry obviously. Using this technique, no matter if you enter too soon or too late, the car will remain very stable. You loose a fraction of time with this, but it sure is very safe. Also, in race condition, remember that 1st chicane is not a point for overtaking, so even if you lift off properly, noone will overtake you there.
As for the very last chicane, I never have problem there. If you wanna play safe, I'd say cut the entry, rather than the exit. I think that's more safe. But also, you can go flat out there without touching the curbs at all, just needs a bit of practice and the right timin/rhythm. You can also use the same method as I mentioned for the 1st chicane. Lif ot a tiny little bit, actually its not even lifting off, just back up on the throttle for a very short moment on entry, say down to 80% or so, and floor it right away.
In the race, I will be avoiding curbs to save tires, and I'm also gonna play safe in chicanes, so I really doubt that 1:16 times will come from me in race conditions.
Btw, what do you want to change on a setup? Just let us know what you would like the car to be like, and we'll post some suggestions as to what to tweak.
Btw2, you mentioned steering settings. I don't know what you changed there, but since you said you are getting a lot of understeer, I assume you moded steering lock/parallel steer/toe settings. Usually more steering angle (directly through lock, or other settings) will result in more understeer.
Anyway, just let us know what you wanna change, and we'll help with that.