I have found no photo evidence that production Ki-43-II kai had lower exiting exhausts like A6M5, all the pictures show them in similar areas to Ki-43-III.
The early A6M5 with multiple exhausts pipes burned its tyres as the lowest exhaust exit was close to the retracted wheels cover. They soon shortened the lowest exhaust so it exited earlier into the air stream, cooling the gases a bit before it came near the retracted tyres area.
It is for this reason I believe the final model 2 Ki-43 (kai or -c, 548kph Gakken) never had lower exiting exhaust pipes, although some book drawings show them as in your picture above. The Ki43 had no tyre door covers so could burn tyres worse than A6M ! I think wrecked Ki-84 were the source of the incorrect Ki-43-II kai exhaust drawings. some even show 4 centre pipes like Ki-84! Also Ki-84 wingtip shape sometimes appears on Ki-43 drawings. The Ki-84 wingtip is more "forward" curved, while Ki-43 is a bit more evenly curved. Wrecked parts of Ki-84 and Ki-43 can be confusing to tell apart!