Passive control is applied to a modern adaptive engine design and its effectiveness compared to an unaltered configuration. The adaptive engine is represented by a supersonic multi-stream rectangular jet nozzle comprised of a core stream (M = 1.6) and bypass (M = 1.0) who merge behind a splitter plate and exit through a SERN onto an aft-deck plate. LES performed at The Ohio State University have identified the splitter plate trailing edge (SPTE) as a highly sensitive region for altering the overall nature of the flow. It has been shown that the shedding frequency initiated at the SPTE acts as a dominating tone throughout the flowfield. As a means for passive control, and an attempt to mitigate this tone, a spanwise perturbation has been introduced to the SPTE and implemented experimentally at Syracuse University. Farfield acoustics and near-field pressure measurements have confirmed the diminishment of the dominant tone for the wavy SPTE. To simulate the nozzle being integrated into an existing airframe, tests are conducted with three different aft deck geometries: a nominal length deck, half nominal, and no deck. PIV of the nominal configuration showed a slight change in the deflection angle of the jet plume. The differences for the half and no deck cases were less significant. These results along with future analyses will be used as a point of comparison between the two splitter plate configurations and act as means to validify the accuracy of the LES.