Road gfxs are also still broken in F-1 Grand Prix Part 3...

Anyway...

r5374 /src/mame/machine/snes.c: SNES: Make the unsupported reads on i/o open bus, fixes (at least) a layer enable in Super Kick Boxing







Technical explaination: uses mode 2, one layer and sprites only and it reads from the TM (bg enable) register. Since it's actually an open bus register that isn't very good for business.