What year is your car, '87? It was possible to order the sill extensions and rear vents from the factory during this period. It was not a "slant delete" at the factory as either option was available separately. The factory also offered "packages" to different markets (SE, LE, 505, 506, etc.) The LE was a factory package offered through the dealers in England that consisted of rear vents, spoiler-oil cooler but without the slant nose/folding headlights (this option also included the higher performance 330bhp engine). 930LE photo below.
The modifications as shown on your car were also replicated by any number of body shops in the 80s and later. Adding the aftermarket rockers and vents were not near as complicated ($$$) as the slant nose/folding headlights/racing valence w/oil cooler arrangement as done by the factory. Your car could be either factory or aftermarket, the genuine factory options would of course be more rare and desirable.
930 LE Pkg:
