Bought an 07 1500 with 4.7 from my grand father with 92k. Good shape, but he's a rancher and pushing 90. Plan is to refurbish and pass it on to my niece. Shortly after the purchase low fuel pressure and knock code appeared. Had the fuel pump replaced this past weekend. Light went off and truck is running fantastic! But on the way home today the light reappeared. I'm baffled. There's no inline filter so what could it be?