The problem with clamping the steering angle sensor is that the value of the steering angle sensor starts all the way at full left and ends at full right which is why when you disconnect the battery or reset something with the module like pulling the ECU or BCM, the car needs to see a full sweep of the steering wheel from left to right to "learn" what those values are and then it needs to see forward movement to "calibrate" the sensor for any variances it may see with forward movement. If you just clamp the sensor, all the steering input to the left or to the right depending on how the sensor is setup will still register. Also, if the vehicle is seeing lateral movement and the steering wheel angle does not correspond to what would be acceptable, the ESP will try to bring the vehicle back "under control" even though you know what you are trying to do with it. The only way to actually get this to function properly is to do it the way Woody did and sever communication on the CAN bus from the YAW sensor to the rest of the car. Even removing power from the module will not completely disable is as I believe that it is getting current through the steering angle sensor and the ground via the mounting of the module to the chassis. I have tried the aforementioned method and it did not completely disable the ESP so voltage was getting in there somehow.

Hope this helps you out.