A friend of mine was cited for "too loud" an engine.  It is now a state requirement to have a BAR referee check if fix-it tickets have been fixed.  His car tested within legal decibels and smog emissions (with no work being done) but one part had a serial number that did not match those on the BAR list for that vehicle so the referee wouldn't sign off the form.  I am confused.  Why is California so worried about whether every part is stock or not?  This was a used car purchased from a guy who works on engines.  My friend figured the car would be in good shape, mechanically speaking.  How do any of us know if the used car we are buying may have a part replaced with one which fits but isn't on some state certified list?  Sounds like the car makers had a friend in Sacramento.