All automakers knew sportscars sales were about to tank/were tanking. It only made sense to maximize profit margins on the ones they were going to sell. Mitsu scrapped all kinds of doodads that the early VR-4 came with, 4w-steer, active-aero, this exhaust gizmo, likely there were others. These things don't sell cars to the general public, not like a HP number does. Upping the HP any low-tech way they could and reducing production expenses by axing these doodads only makes sense given the position they were in back then.