boeing7873

I have been battling with PETG quality issues. Mostly under extrusion, poor adhesion, and oozing. I can pretty much solve all issues on small test objects, but when I slice my current project, a 12 hour print, problems surface in many areas. Oozing, sometimes a random layer under extruded, blobs in random places... much of the oozing happens in the support. What can change from small to big objects? Thanks!