DCFIFO and AD9433 problem

Here's the thing, I'm only using the DAC to see if the ADC output is as expected or not. The write clock of the FIFO is at the same frequency as that of the ADC clock (but shifted by 180 degrees) so I only write every new data coming out of the ADC once. Is there something wrong with this?

The problem is, why would the output of the ADC (as viewed from the output of the DAC) change when the FIFO is connected?

Is this some kind of loading effect or something?

Do I need to do some kind of buffering or something with the ADC output?

Thanks guru. Appreciate the reply.