Fuel Pressure issue
I have a stock 2006, 6.0L. For the past couple months, I have noticed a lack in power and my fuel milage has gone in the toilet. I couldnt figure out what the problem was, so I finally took it in to my dealer. Got it back yesterday and was told that the fuel pump wasnt sending enough pressure and as a result, I now had 4 bad injectors. They replaced the pump and injectors. I picked up the truck yesterday and drove it home. For the first 40 or so miles, it ran great. Power was back, everything ran smooth, fuel mileage was back to where it should be. Then within a couple minutes, everything seemed to go back to where it was before I took it in. Truck ran rough, decrease in power... My fuel filter only has about 6000 miles on it, so it's not that....I'm wondering if the Fuel Pressure Regulator spring could be worn. Any ideas?