The muffler is not an Emission Control Component. The muffler you need to use must be an OEM (original engine manufacturer) part; as opposed to an EO (executive order) part. Mufflers, since they located "post" the Catalytic Converter and rear oxygen sensor will not be issued an EO number, but the muffler you use must be designed for use on your Toyota pickup truck and must be to OEM specifications.
Search and locate a OEM muffler for a 1992 Toyota Pickup and have that documentation on hand during the smog check. OEM does not mean the muffler has to come from Toyota, it just means the muffler must be designed exactly as the Toyota part and approved by California for use on your specific model of Toyota truck. We recommend using a 1992 Toyota Pickup muffler simply because of your trucks chassis design. It is possible that another model years muffler will not fit on your 1992 Toyota.
If you have further issues with the smog check referee which you visited we recommend contacting a second smog referee for clarification, or contact the BAR directly at (800) 952-5210.
