Combine giblets, neck, and 3 cups water in a saucepan. Bring to a boil; cover, reduce heat, and simmer 45 minutes to 1 hour or until giblets are tender. Strain, reserving broth. Discard turkey neck. Coarsely chop giblets; set aside.
Add reserved broth (2 cups) to turkey pan drippings; stir until browned bits are loosened from bottom of roasting pan.
Transfer broth and drippings to a saucepan, if desired, or continue cooking in roasting pan placed over 2 burners on the stovetop. Stir in chopped giblets, if desired. Bring to a boil; reduce heat, and simmer, uncovered, 3 to 5 minutes.
Combine flour and 1/2 cup water, stirring until blended; gradually stir into gravy. Bring to a boil; boil 1 minute or until thickened. Set aside some plain gravy, if desired. Stir garlic powder and bourbon into remaining gravy. Serve hot.
Fix It Faster: Substitute canned chicken broth instead of making homemade broth, if desired.