I am using Cura version 15.04 on Linux (and some times MacOS). You set me on the right track though. I just built this printer and the Z0 position was too far down so to compensate I was setting my first layer height at 1mm when it should have been around .2 or .15. I knew from the G code that setting the first layer at 1mm would get Cura to shift the start position to Z1 but I didn't realize that it was also increasing the extrusion rate. I compared 2 G code files, one with the layer height at 1mm and one with the layer height at .15mm and the latter's extrusion rate is far more reasonable. Thanks for the help!