help I have starting issues

[cuttin it up]

I have a 01 4.0 v6 ranger 4x4 and im having starting issues. When the tank is full it stars normal but as the tank gets lower it gets harder to start. by the time I get to a 1/2 tank im crankin it even after the doors lock on there own. I got a check engine light and its for low flow on the egr system. if any body has any suggestions or had this problem any info or suggestions would be cool thanks