So I've been trying to do as much reading as I can on adding one of these two options to replace my stock pump. Although I think I understand most of it. . still a little confused as to remove fuel heater ect. . think I'm going to leave it all in place. . anyhow my question is which of these two is the easiest to install? They both appear to do the same thing... and if I'm reading correctly the fass seems like a complicated install? Am I missing anything? Exactly what do you have to do to install either one of these?