How do you use the bugs that you find while testing to get more attention to refactoring and improving the overall code base and re-writing particularly troublesome sections of code that have been proven as buggy, hard-to-maintain or poorly written?
You might consider establishing unit tests (NUnit,XUnit,JUnit,etc...) in more troublesome places (or a seperate project) and once sufficient tests are in place inact some form of continuous integration to auto-run the tests in some form of pre-commit hook. Using Jenkins for example, you can track some metrics which will give you some fire power on the importance of refactoring poorly written code. In other words, you want to be able to say confidently "X hours are spent monthly fixing bugs in location A. The total number of bugs found in location A is Y. Therefore, I recommend fixing location A."