guys i was just wondering, lets said i have the following item in my car right now:

intake
header
exhaust

and if i was to go smog check do i have to put the stock item back in or can i just leave it like this and go smog check?

So far i have an intake in my and i was thinking of getting other stuff next.

 

a catback wont affect smog at all
and you will be able to pass smog if you have the oxygen sensor thing for the header and your intake will need the sensor thingys too
when you buy the mod, it will telll you that its "Fully 50-state street legal and CARB exempt", or something similar to that
and keep your stock catalytic converter so you can pass smog

 

You must have the exemption sticker for the intake and header viewable. since the EO number on it has to be recorded on the smog inspection.

 

so lets said i dont have the exemption sticker cause my intake is from ebay (30 bucks) so in order to pass smog i have to put my original intake back on?

 

I think the answer for any of this depends on where you live. California? If so then you should probably put the stock intake back on because that's real easy to do. Every other state has different rules & different ways of doing things.