Years ago, I used mutation testing in a pretty big Java project. Let me tell you: You don't want so much coverage. It's usually a waste of time and makes changes to existing code very annoying. Keep mutation testing/high coverage for a small selection of _very important_ code, but don't overdo it
But did it lead to the finding of additional bugs?
It's very likely that over the years, it found something. But we didn't have anything to compare against, because it was always mutation testing from day one.