Piston oilers
Thicker piston domes
Orings
Knife cut billet crank
Dry sump
Aerator

Whenever I asked any engine builder about O rings I always get a weird look and a no . Hmmm.

when I saw the big cams out of Supercat engines at very well know Michigan engine builders dhop he told me that they see the rear cylinders retarded a couple degrees from a std cam actually twisting under load. They make more power with the larger cam.