Comprules look like this:
YYYYXXXX
where XXXX and YYYY are of the form RABC
where R is the comprule and A, B and C are
the components used by the rule.
XXXX chooses the first component, YYYY chooses the second.
All digits are hexadecimal (0-9, A-F)

If a comprule is valid, it is used to choose a component for a vehicle.
Otherwise a component (or none, with a probability of 1/3)
that is not used yet is choosen at random.

Components 0-E (hex) are valid and considered by the rules,
F is an invalid component. However only up to 6 components
are actually supported by the game.

Valid comprules are
III: 1, 2
VC: 1, 2, 3, 4
SA: 1, 2, 3, 4

Comprules 1 and 2 are the same but 2 is only valid at rainy weather.

1/2: Choose one of the three components in this rule
3: Choose one of the three components in this rule or none
4: Choose one of components 0 to 4, arguments are unused