All the servos or just one? If it's all of them, then it's probably your battery pack. If your using 4 rechargables in the holder, they won't put out enough voltage to really move the servos well. If your running 4 alkiline's, put in new ones and see if it helps. Best bet is to get a 5 cell rechargable hump pack for it. Then you get 6V's and plenty of current.
Stock servos aren't that fast to begin with.
If it's just your steering servo, then check your pivot balls that the axle blocks pivot on. If the caps are too tight, they cause binding which makes the servo move slow.