Hi Zane.
How long have you had the mount and has it always had this problem? I've successfully imaged for 3 min unguided at times. If you drift is in DEC then I don't see how it can be anything other than polar alignment. There is no PE in the DEC axis as the motor doesn't operate unless a correction is applied during guiding. Its a passive axis.
How do you polar align your scope? Drift or polar scope? Have you tried K3CCDTools to help drift align.?
Is you scope well balanced fore and aft on the Dec axis? If not how tight is your dec clutch. could it be slipping unddr off balance weight?
There is one other thing I can think of, and the only way I know of how to check it is to use an Argonavis with the latest TPAS upgrade. If you have always had the problem you may have a non-orthagonality problem with your Dec axis and mount head. I had this problem with my GM8 and didn't know it until Gary and I were trying to get my Argo to work and we couldn't get good accuracy. We tested with the new firmware (beta then) and found a non-collimation issue (nothing to do with mirrors) that wouldn't allow me to get an accurate polar alignment or drift alignment, even if it looked like it in K3. That's about the only other thing I can think of.
