I've been losing prime below a quarter of a tank. So I rebuilt the filter head and it was all fine. I also installed a lift pump and put in a new fuel filter. The problem continues to happen, but only below a quarter of a tank. I can get it to run if i reprime the system and the low fuel light does not come on. I can go about 2.5 miles before it does it all over again. I dont have any fuel leaks because i would've found them by now. I get a p0087 and p1093. Both are low fuel rail pressure. I am at a loss. I haven't found any threads on this. Anybody have suggestions or experience with this problem. Do I need to rebuild the frpv or install a shim? Would the fprv effect my mileage, too? Because I am getting horrible mileage (14mpg).