They don't need replacing, If you didn't know, the 98 fuel rails will not accept an aftermarket adjustable FPR because the stock one is welded to the rail. However the 96-97 4.6 fuel rails will accept one. So that's why I was wanting to change the rails out sometime. Being able to change FP is a good thing to be able to do.Custom2kGt said:Unless yours absolutley need replacing they should be good for at least 350 hp. That's what I've read in 5.0 anyway. With the mods listed I would have to ask why are you wanting to change out your fuel rails?