We define a mechanism for specifying performance queries which combine instantaneous observations of model states and finite sequences of observations of model activities. We realise these queries by composing the state-aware observers (called eXtended Stochastic Probes (XSP)) with a model expressed in a stochastically-timed process algebra. Our work has been conceived in the context of the process algebra PEPA. However the ideas involved are relevant to all timed process algebras with an underlying discrete-state representation such as a continuous-time Markov chain.