I have a 06 C5500 keeps tripping P0087 code Low Fuel Rail Pressure. I have replaced the injectors, fprv, and fuel supply hoses from the tank, and the fuel filter several times. I was told I could delete the P0087 with a efilive controller and my truck would be derated slightly but would not go to limp in for the low fuel pressure. I have spent $7000 dollars on truck and can't get rid of the P0087 code it occurs after engine reaches operating temp and will go to limp in under load on any hills or a strong head wind. I need some advice thanks.