United Plugins recently updated all of their plugins adding the intelligent sleep on silence function. That includes DIFIX which has just received another update (to version 2.1) that fixes a few internal compatibility bugs.
DIFIX repairs guitar and bass tracks that were recorded without a proper DI Box.
The sleep on silence function intelligently detects whether it makes sense to perform processing at all. And if not, it temporarily switches the plugin to sleep mode. In such a state, it requires virtually no CPU at all saves the computing sources for other processes and plugins.