Method for improved performance of a vehicle

An engine control system for managing lean NOx trap (72) decontamination uses associated fuel economy impacts to determine when decontamination is enabled. In particular, a maximum achievable benefit provided by lean operation with a decontaminated NOx trap (72), a present fuel economy benefit being provided by lean operation, and a fuel economy penalty for performing decontamination are used. When a resulting benefit is greater than a penalty, decontamination is enabled.