I'm going to guess that the OP has this type of post...
As do I. I was also getting a creaking and popping noise. It would creak when pedaling and going over rough pavement while I was seated. Un-weighted, the creaking would stop. The popping would occur when I weighted and un-weighted the saddle. I swapped the post for the carbon one that came on my old Allez (no zertz) and it seems to have solved the problem for now. The shop swapped my old post that came with the Tarmac for a new one but I have yet to try it out.