They are usually held on with plastic rivets, but some also have 3M 2-sided tape adhesive. If yours is just the rivet type, go and buy replacement rivets (Ford dealers stock them) first - do NOT re-use the old ones, they are damaged by removal and you WILL end up losing the scoops at some later date (probably at high speed). Some folks add the 3M sticky to compensate for recycling rivets, but I think this is a false economy (and removing them AFTER adding a bunch of glue becomes a harder chore).
If yours has the glue, I start by softening everything (a hot day will often do the trick, since it is summer, but a careful application of a hair dryer can be beneficial), and using monofilament fishing line.
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