valvetrain noise 5.9 magnum

Chances are it's a lifter getting tired. Not a big deal but 25K of hard miles will wear them faster. You can try a longer pushrod to get more preload but IMo it's more like you need to replace the bad one(s). Which is hard because you don't know which ones are bad on that side. If you're thinking of upgrading it might be a good time. Otherwise it's not fatal.