legal/illegal questions..., wondering what's "legal" Options

[MaskedMan]

Alright, well i have a few questions on what is or isn't illegal, and was kinda hoping someone would know or have any information on the subject. I live in LA, and i was just kind of wondering what mods are actually illegal.

Engine mods. I heard many different things like, ANY engine mod is illegal including a short ram intake. Can anyone add to this?

Are cars required to have mufflers? Cause mine was kind of hacked off and stolen off my car while i was away. Car now stays in my garage until i go back.

Nitrous Oxide. Is it legal to have it hooked up in your car?

RHD conversion, Legal or Illegal?

Dark window tint. what is the legal limit? i've seen some pretty dark tint on all of the windows.

Changing to an aftermarket steering wheel.

Front license plate. Are they required?

And i've always kind of wondered but is underglow completely illegal, or is it just red and blue underglow that is illegal?

Ok any help would be great, im just kind of curious about this stuff, cuase i hear it debated all the time, but i never get a clear answer.