A plug connector includes a plug body having a terminating end terminated to an electrical component and a mating end mated with a mating electrical connector. The plug body has first and second outer sides. The plug body has pockets between the first and second outer sides. A plug shroud extends from the plug body at the terminating end that is configured to be coupled to the electrical component. A contact array is held by the plug body and includes signal and ground contacts. The signal and ground contacts are exposed along the first and second outer sides. At least some of the ground contacts are aligned with corresponding pockets. Resonance-control lossy inserts are provided in corresponding pockets adjacent corresponding ground contacts. The lossy inserts are manufactured from lossy material capable of absorbing electrical resonance propagating through the plug body.