to combat smog which results in a max. octane rating of 91 for premium fuel (briefly 92 in 2003 and 2004). So in the interest of safety, Cali JWT ecu's are set for 91 to prevent detonation. Ash also offers an "A Class" to accomodate this as well. A rep from JWT informed me of this in early 2004 when I was interested in purchasing a chip. Since most of Cali's gas still maxes out at 91 I would assume this is still the case.