you can have mods but they need to be certified by california aka C.A.R.B. if your parts are CARB certified then they usually come with a sticker or something so that the smog guy knows its approved. without this sticker they will fail you on visual inspecition no matter if your car passes emissions. also the emission test is pretty strict, so you car needs to be in good order..took my 2001 gsr like 3 times to pass smog. those cars in magazines are illegal and probably have hookups when it comes to smog...CALI smog sux