Sensor Error Adjustment
You can calibrate the sensors with a measurement at x=170 using a power exponent to the interpolate the curve.  Other errors may be due to hysteresis, loose connections or noise.

I plotted the average to be \$y(x)=-0.0000656*x^{2.573}, R^2=0.995\$  

But better results can be obtained curve-fitting with 2 or more measurements.