What EPA compliance is required for JDM imports?

For vehicles 21 years old or older, you file EPA Form 3520-1 under the "21-year exemption" — no emissions modifications are required. For newer vehicles, the car must meet current EPA standards, which almost always requires modifications by a Registered Importer. In practice, most enthusiasts wait for 25-year eligibility (which also covers EPA) rather than dealing with compliance modifications, which can cost $5,000-$15,000+.