As you go through your list of firewall rules and update your documentation, you may find that you have more than one rule serving the same purpose. If you can eliminate one of those rules or combine some rules to be more effective, that can speed up your network.
Similarly, you may find that some of your rules are never applied because none of your traffic meets the specific criteria outlined in the rules. Consider whether the rule is really necessary. If not, deleting it could lead to performance improvements.