Like I said, be patient... After a few applications, the spots will slowly disappear, along with swirls.

To prevent new ones, always have a nice coat of wax on there, and dry the truck as soon as possible after it gets wet (from washing, really - since it's clean).

One thing you might want to try is washing off the truck with a hose and drying it if it's been out in the rain or something, sitting. Sounds like you might live in an acid rain environment.

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01 SE 6cyl 5spd Solar Yellow