While still on the subject of x68k racing games, super hangon for the x68k seems to have a different issue, one with background colours often being rendered as black rather than as they should be. This means the music select screen has a black background, when it should be orange, and parts of the sky are black too. Had that one just been the sky, I would have guessed raster split too, but because an entire screen has the wrong background colour, I'm not so certain
This part is caused by apparently the hardware selects the lowest priority tile layer pixel to draw if all layers are transparent.
This one by the 0 color index being treated as transparent which as I recall I assumed was true based on other behavior but nothing expects it (at least nothing I know of... ).