Which vehicle modifications are considered illegal, and what are the consequences?

Yes, there are illegal vehicle modifications. The most popular ones are:
- Tinted windows 
- “Smoked” headlights
- Red lights on the front of your vehicle
- Uncovered light bars
- Vehicles with headlights that are lower than 24 inches from the ground
- License plate covers
- Retractable license plates
- Flashing "underglow" lights
- Removed mufflers or mufflers with a cutout or bypass to make the car louder
- Any tampering with emission controls including your catalytic converters

You can be ticketed for any one of these modifications. Additionally, auto insurance policies do not cover vehicle modifications or customizations in their standard contracts. Typically, an auto insurance company won’t provide coverage for “enhancements” to vehicles, with the exception of aftermarket tires and rims. Most insurance carriers provide an option for supplemental coverage.

Do not hide modifications from your insurer – they may not only deny a claim for enhancements/modifications that they were not aware of, but they could go as far as to void/cancel your policy due to non-disclosure of the customizations which can constitute a material misrepresentation.