Combine light brown and white sugars, water, corn syrup, and salt in a heavy 2 quart saucepan. Cook covered until mixture boils rapidly. Remove lid, place candy thermometer in pan, and cook without stirring to 260 degrees F (127 degrees C). Remove from heat.
Beat egg whites until stiff. Pour hot syrup in thin stream over egg whites, beating constantly with electric mixer on high speed. Add vanilla and pecan flavoring.
Continue beating until soft peaks form and candy starts to lose its gloss. Stir in pecans and drop by spoonfuls onto waxed paper. When candy has set, store in airtight container.