I just did some INL runs, and the results are pretty interesting. I think the sawtooth like shape means that I got the calibration constants for the residue ADC wrong.
My calibration scheme is as follows: Disconnect input from the integrator, turn on +ref for 1/16 of a runup cycle, measure residue difference to obtain a 'runup-down' (RUD) value, then turn on -ref for 1/16 of a runup cycle, measure difference to obtain a 'runup-up' (RUU) value, and use them in the formula I posted above.
Update: there was an error in the runup math, INL after the fix is also posted.