I blogged about this Fourth Circuit case earlier this year, but I must have skipped over the Rule 106 discussion. The defense attempted to enter a witness's full police statement into evidence using 106, but the court denied that because the parts that weren't admitted were inadmissible hearsay. This case could be a big shift (or clarification) for the Fourth Circuit because it could mean that this circuit is now in the "procedural" camp of 106. See these posts for more clarification: here and here.
Professor Bellin clarified some of the issues with prior precedent on 106 from the Fourth Circuit: