Well, if the manufacturer coughs up extortion money, aka CARB, then you can run aftermarket equipment. However, I think most places would be OK with the visual, so long as the obvious is there (air filter box, no tubular header, etc.)...Smog nazis didn't say anything about my huge intercooler or SS piping, but did fail me (visually) on the air filter cone, although they still tested it anyway; go figure. It didn't pass only cause it couldn't hold the 30 second @ 2500 rpm test (iirc) [check engine light], due to some weird condition I ended up fixing. I have an aeromotive AFPR and am not concerned about failing for that.