It's not a tailpipe issue Jonny. It's California's fixation with not allowing any visual mods either without an exemption order number on the part or a trip to a referee. I think if it passes at the pipe the hood doesn't even get opened, after all we are only concerned with the pollutants, right?
For example, you cannot move the location of the cats, or their number. My truck comes with 4 cats and to keep them in their factory location will be virtually impossible with a single turbo. If I re-locate them at all, even though I keep all of them it is illegal. That plus a turbo sitting where a blower came from the factory will cause "issues" with the visual portion. There may be a way around it hopefully. I have NO problem keeping all the smog equipment intact and functioning. Just give me a bit of leeway to package the parts.
Jody