Extrusion inconsistencies

I really don't understand why, but when printing Overture PETG I'm getting very inconsistent extruding depending on what it's printing. Walls? Relatively decent. Anything else? Absolute gsrbage.garbage. The stringing I can deal with, though it isn't ideal. But my supports are looking terrible and my infil isn't much better. I don't understand why, as there's no difference in my speed or anything else with the exception of bridging but there's none of that in my pictures. I've got it running 55mm/s, cooling fan on 40%, running 235 nozzle temp.