Stepper motors clicking while printing

Hi all -

I am working on getting my first printer together. Its a delta-pi using RUMBA electronics and marlin firmware. I have everything together and it seems to auto home correctly. The steppers run smooth when going to home but when I tried to do an "air" print the steppers click a lot and have really jerky movement. I used repetier and slic3r to make the g-code and I think I have all the settings correct for my delta. Also, after each test I need to re-tension the belts because they pull through. They only need re-tensioned when it is clicking.

Any suggestions?

Clicking: [dl.dropboxusercontent.com]

Not clicking: [dl.dropboxusercontent.com]