ADS8320: ADC Accuracy Issue

I was referred here by TI Customer Support. I have been validating a new product of ours that uses the ADS8320E/250 ADC and I am having some problems with the accuracy. When I graph the input voltage going into the ADC and compare it to what I read on the output, there is a mismatch in the shape. This is pointing to an issue with the ADC itself. I would like to send a TI apps engineer a spreadsheet of my results (with a better description of the problem) and the schematic pages of our design.