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A method for improving three-way catalyst (TWC) performance by superimposing a low frequency lean air-to-fuel ratio (AFR)bias perturbation onto the standard AFR oscillations is described. This observation of Catalyst Regeneration (CatRegen) has been attributed to a reactivation of poisoned precious metal sites on the catalyst surface. Preliminary tests under steady-state conditions show that there is a gradual reduction in TWC activity for NOx after a lean-rich transition, suggesting a temporary poisoning of the active precious metal sites on the TWC under rich conditions. This deactivation can be prevented by periodically exposing the catalyst to lean exhaust gas; which has led to the development of the CatRegen system.