There are a number of things that it might be, but the returnless fuel system (which you have) is well known for problems of fuel starvation caused by a plugged filter screen on the fuel pump module. The screen is too fine and too small. It can be removed and thrown away as there is still a conventional sock filter before the pump inside the pump module.
Check out the FAQ for changing the returnless fuel pump for instructions for access to the pump. The instructions are the same except you don't need to replace the pump (most of the time). The filter screen is shown on the very last photo on the page.
