William Hurst appeals his conviction under the Motor Vehicle Theft Deterrent Act. For the reasons set forth below, we will affirm.
I.
Because we write primarily for the parties, it is not necessary to recite the facts or procedural history of this case in detail. It is sufficient to note that Hurst was indicted for conspiring to altering or removing vehicle identification numbers and trafficking in certain motor vehicles or motor vehicle parts, in violation of 18 U.S.C. §§ 511 and 2321 respectively. He was thereafter convicted of those charges following a bifurcated jury trial. During the second phase of that trial, the jury found several sentencing factors, and Hurst now appeals from the judgment of sentence that was imposed based upon those findings.
II.
Hurst raises several arguments on appeal, many of which merit only the briefest comment, and we therefore dispose of them in the margin. He argues that the government: wrongly obtained evidence through the use of post indictment grand jury subpoenas that were not properly served;1 failed to produce a required Schofield affidavit; should have been com*135pelled to turn over rough notes of the FBI agent;2 and that the government improperly withheld selected material from the defense during the discovery phase. He also claims that: the government’s expert testimony was unreliable and insufficient to sustain a conviction;3 the district court improperly denied defense attempts to play audio tapes and the government misrepresented those tapes during its closing; the jury instructions were incomplete or insufficient;4 and the sentencing factors should have been stricken from the superseding indictment and not presented to the jury.5 Lastly, he challenges the court’s forfeiture order.
The arguments not addressed in the margin are briefly discussed below:
A.
Hurst’s challenge to the district court’s refusal to quash the grand jury subpoenas is based upon his continued claim of a Fifth Amendment privilege against self incrimination, misuse of the subpoena to obtain evidence relevant to a prior indictment, and a claim that the government failed to furnish a Schofield affidavit.6 We have already disposed of the argument that post indictment grand jury subpoenas are improper. See n. 2, swpra. Hurst’s *136remaining challenge to the grand jury subpoenas is also meritless.
“[T]he law presumes, absent a strong showing to the contrary, that a grand jury acts within the legitimate scope of its authority.” United States v. R. Enterprises, 498 U.S. 292, 300, 111 S.Ct. 722, 112 L.Ed.2d 795 (1991). Here, Hurst has made no showing to the contrary, let alone the “strong showing” that is required. The district court heard Hurst’s challenge to the subpoenas, and properly concluded that he had not sustained his burden of showing that the subpoenas were unreasonable. See id. at 301, 111 S.Ct. 722 (“[A] grand jury subpoena issued through normal channels is expected to be reasonable, and the burden of showing unreasonableness must be on the recipient who seeks to avoid compliance.”).
The second and third post indictment subpoenas were valid because they sought information that could be useful in the ongoing investigation. Even now, Hurst appears to suggest that it was somehow unreasonable or inappropriate to subpoena the records for his business because it no longer existed, and that the records in question were somehow protected by Hurst’s Fifth Amendment privilege. Yet, defense counsel concedes that the records the government introduced from the Pennsylvania Department of State “undoubtedly” showed that the corporation had never been dissolved. See Appellant’s Br. at 15. Counsel fails to appreciate that the absence of any “further tax obligations to the Commonwealth ...” does not undermine the validity of the subpoenas that were issued for the corporation’s records or cloak them with a Fifth Amendment privilege.
B.
Hurst also tries to obtain relief from the fact that the government inadvertently disclosed some of its work product to defense counsel during discovery and then removed that material from the items that were made available to defense counsel. The government was properly allowed to withhold certain inadvertently disclosed documents from the defense during discovery because those documents were work product. “Reports, memoranda, or other internal government documents made by an attorney for the government or other government agent in connection with investigating or prosecuting the case” are not subject to discovery. Fed.R.Crim.P. 16(a)(2). The district court correctly concluded that Hurst has not established that the government’s actions were improper.
C.
Hurst argues the district court erred in not allowing the jury to hear certain tape recorded conversations involving Jarosz and Chomyn. The district court ruled that the evidence was extrinsic and therefore inadmissible under Fed.R.Evid. 608(b). At trial, defense counsel proffered that the tapes were admissible to show “[a] title in exchange.” App. at 392a. The district court recognized that the government was not attempting to show that Hurst received title. Rather, the government was trying to show he hadn’t received title. Hurst now argues the tapes were admissible because “they could have cast doubt on the government’s conspiracy theory that the defendant, Jarosz, Chomyn and Watts were all in one conspiracy....” Appellant’s Br. at 37. That was not the proffer originally offered at the trial, and the trial court did not abuse its discretion in rejecting the proffer that was offered.
We also reject Hurst’s claim that the government’s closing arguments misrepresented the audio tapes. Extrinsic evidence used to attack or support a witness’s *137“character for truthfulness” is not permitted unless that evidence is a conviction of a crime pursuant to Fed.R.Evid. 609. Fed. R.Evid. 608(b). This limitation serves to avoid “mini-trials” and jury confusion stemming from introduction of collateral matters. Carter v. Hewitt, 617 F.2d 961, 971 (3d Cir.1980). During its closing, the government simply explained why some audio tapes had been introduced while others had not been. We see no merit to Hurst’s challenge to that closing.
D.
Hurst’s challenge to the order of forfeiture is also meritless. The district court recognized that it had initially faded to include forfeiture in the judgment of sentence and properly granted the government’s motion to include it pursuant to Rule 32.2(b)(3). The court acted appropriately in doing so. See United States v. Bennett, 423 F.3d 271 (3d Cir.2005). During trial, the government proved the required nexus between the amount forfeited and the value of the automobiles alleged in the superseding indictment as is evident from the jury’s finding that the value of the stolen cars was $114,000. Forfeiture was correctly ordered. See 18 U.S.C. § 982 (2002).
III.
For all of the above reasons, we will affirm the district courts judgment of sentence.