what were you are before?

Assuming you went heavier all around (say you were at 10-10-5) I can see it being more loose for sure in the rear.

As for the servo, if you mean that it feels like too much throw at too little input, try putting in some negative expo on the steering. I use this on all my fast servos as it calms down the low end response. I run anywhere between 10 - 20% depending on the car and servo.