What are the car modifications that are considered illegal or legal (according to the law)?

From what I know, the following are illegal (correct me if I'm wrong peeps!)

1. Wang-wang or sirens
2. Blinkers
3. Tail lights to a different color other than red
4. Personalized plates / hard to see plates
5. Heavy tint (diba dati bawal ang tint during the Marcos era?)
6. Headlights (I remember someone telling me that this is up to a certain intensity?)
7. Anything else?

I've been reading through the threads, and I'm getting confused, since it appears that what's legal not is overlapping already.

And if its illegal, why do people insist on using / doing it?