How do I fix a slow fuel pump

Sound like the fuel pressure regulator or possibly a partially clogged fuel filter but more than likely it is the regulator.

If it's the original pump then it's probably near the end of it's working life. Imagine if you had a daughter when you bought the truck, then you would more than likely be a Grandparent today

Get a gauge and check the pressure being delivered to the regulator. Key on, engine off. Note the pressure when you initially turn the key to the on position. If it takes a while to build up pressure to spec, suspect a clogged filter or bad pump. If you suspect a regulator problem remember the regular is a mechanical device, not electric or electronic. It, by itself, does not send OBD codes, but could affect things like oxygen sensors readings which could throw a code.