Guides and questions
Plain-language guides to EOs, part numbers and keeping records.
EO basics
Vehicle guides
Part types
- How to find the part number on an installed part
- Manufacturer fitment vs. EO coverage
- Cold air intakes and California smog checks: what to look up
- Aftermarket headers and CARB EOs: what to look up
- Cat-back exhaust vs. emissions-related modifications
- Aftermarket tuners: what to look up before a smog check
- What to do if you can't find your part number