In what circumstances will a federal judge vacate or vacate an improper portion of a sentence?

At the same time, we have neither a desire to prevent the court from imposing any sentence that is lawful nor any wish to cause unnecessary prolongation of proceedings in the district court. Accordingly, we have on occasion given the district court the option simply of eliminating the improper portion of its sentence. See, e.g., United States v. Khan, 869 F.2d at 662. And in some instances we have remanded for the court to impose whatever sentence it chose within the original range of permissibility. See, e.g., United States v. Young, 932 F.2d 1035, 1038 (2d Cir.1991) (fine not imposed originally, in order to give priority to restitution, might be imposed on remand in view of the vacation of the restitution order); see also United States v. Leonard, 37 F.3d 32, 37 (2d Cir.1994) (finding departure inadequately explained, and vacating entire sentence "in order to give the district court complete flexibility upon resentencing").