Combine guava jam, lemon juice, soy sauce, allspice, salt, and pepper in a saucepan over medium heat. Cook until jam melts and mixture is blended.
Stir together water and cornstarch; stir into guava mixture. Bring to a boil, and boil 1 minute until thickened. Remove from heat, and cool.
Place chicken in a large zip-top bag; pour 1/4 cup sauce over chicken, tossing to coat. Cover and chill 1 hour or overnight.
Place chicken in a large roasting pan. Bake at 350° for 30 minutes; drain liquid.
Pour remaining sauce over chicken. Bake 15 minutes or until golden brown.