Well I have no idea what your definition of "huge" means but on a 31,000 book library I have no issues - the search runs in a couple of seconds without problems.
The only thing that has changed in that part of the code would be for fuzzy *author* searches, for which I no longer generate reversals of author names which helps reduce the number of false positives. However that will have zero impact on fuzzy title searches.
How many exemptions do you have setup? Has your "cleaning up" process involved adding to those? Select "Show all book duplicate exemptions" to see what you have. You can clear the exemptions by selecting them and choosing "Remove selected exemptions". See if that helps you out.