2001 GMC Yukon

Does anyone here think that it is possible for the fuel pump or the flexible plastic hose from the pump to the outlet on the tank to be sucking air? Because, when our tank gets to 1/2 tank full the service engine light comes on and it does not run very well. We had it scanned and the code came back as System too lean. Was suggested that it was the Oxygen sensor but I feel that it could be the fuel pump itself. I got the fuel pump. Any suggestions or comments appreciated. When you fill the gas tank up it is fine until it gets to 1/2 tank or less.

I don't think it's the o2 sensor, If it only sets the code when the tank is half way empty. If it was the o2 then it would give you the code, even when the tank is full.
I have the same problem with my 96 yukon.
Let me know, If you had figured it out.