My initial reaction to the photo was exactly the same as Rickshaw's, but having lookied at the others, I now believe the "photoshopping" to be an optical illusion caused by some unusual features of the exhaust installation:
1. The exhaust is polished while the rest of the aircraft is cammo, so it's a completely different colour from everthing around it. It's sides also point downwards, reflecting the ground and colours that don't appear on the airframe, adding to the effect.
2. The aperture in the cowling around the exhaust is edged with a strip of unpainted metal with a line of rivets in it. This creates the illusion that the exhaust is "disconnected" from the rest of the image and has a pixellated edge.
3. Your brain wants to believe that the exhaust is oval, so the sharp cut-off at its trailing edge comes across as crude photshopping. However the exhaust isn't oval: it has an asymetric teardrop cross-section, so the sharp cut off at the trailing edge is correct.
4. The exhaust's internal section is not the same as it's external one, creating a thin, horizontal triangle at the rear corner. However this triangle isn't 100% flat, and in the pic, it's reflecting sunlight very strongly, creating a thin white line that again, appears to separate the exhaust from the image around it.