Industrial companies have to continuously improve their performance, which is defined in terms of numerous and multi-level criteria. According to the Deming wheel principle, decision-makers need to be provided with sound and pragmatic improvement methodologies, supplying operational tools for the objectives' definition, the action choice and the performance expression. Based on the generic PETRA methodology and using an established performance model that expresses overall performance by aggregating elementary ones, this article is a contribution to the decision-makers' information needs. By considering performance as a satisfaction degree of a given objective, we particularly focus, here, on the improvement of an overall performance, and thus on the choice of the right opportunity viewed as the best subset of relevant actions among the set of potential actions. Therefore the notion of action impact on the elementary performances is defined. Then the problem of the impact of a subset of actions on the elementary performances is posed and several ways are proposed to deal with it. Lastly the subset of actions impact on the overall performance is defined by a performance aggregation model. The proposed approach is applied to a case study submitted by an automation component manufacturer.