I would think you could edit the particular wave file/files that need fixing, and then replace the original file or files with your edited ones. You would want to back up the original ones, just in case your perception of 'lag' may have been tempered by a good stout round of ale, hee hee. (It's always good to create a way to restore the original content, in case there is some other factors to consider, or whatever.
So lots of audio wave editors out there, so it shouldn't be much of a deal to accomplish some minor editing to fix something like you are seeing for some factory provided sample content.
Good luck with it all,
Bob Bone