Any kind of off-road Y-pipe, H-pipe, X-pipe or any configuration is illegal if the catalytic converters are eliminated.
This is not just true for California, but any state that has smog laws.
It is also true nationwide on any vehicle that came factory equipped with catalytic converters. The federal EPA laws make it a crime to tamper, alter or otherwise remove pollution control equipment from those vehicles so-equipped.
Of course, the typical Catch 22 of this legislation, as is true of most legislation, is that there are always exceptions.
Thus in most states, including California, you can replace the OEM converters with aftermarket converters just so long as the vehicle passes both the visual & sniffer inspections.
However, the flip side of this is trying to find someone who will replace catalytic converters if they are not either inoperable, malfunctioning or the vehicle has surpassed the legislated time of ownership in either years or mileage where replacement is allowed.
Any business who agrees to replace such items are themselves liable for violating state & federal law so many will obviously refrain from doing so, while others knowingly & willingly accept such a risk.
By the way, the comment that it is illegal in California to make any exhaust modifications is incorrect. I have an aftermarket cat-back exhaust on my Saleen that was installed in 1991 that is perfectly legal as is my aftermarket catalytic H-pipe due to the codicile in California law that allows certain aftermarket modifications if the manufacturer has received CARB approval by proving it performs an identical function as the OEM piece it replaced.
1999 SVT Contour, #2140 of 2760, Tropic Green - Medium Prairie Tan
Koni Sport struts; TSW Blade wheels; Nakamichi, a/d/s/, Boston Acoustics, Infinity I.C.E.
1989 Saleen Mustang, #89-0408, too many mods to list here
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