I've seen it mentioned in many threads, and it confuses me. What exactly is it, and whats the difference?

Sorry for the n00b question.

 

cali spec means the cars exhaust meats the cali specifications, which are a little more then fed spec. one main diff in the 5th gen is the number of O2 sensors we have. a fed spec only has 3 while the cali spec has 4. hope i helped.

 

ahh ok. Thanks alot man.

 

funny thing, i live in cali and my cars a fed spec...also how some people outside of cali have cali spec maximas...doesnt make much sense to me