Trying to research about ECU tuning, a couple of questions
 

is it correct that I can pass the california emission test if I keep the stock tune as one of the maps? I wanted to go E85 but don't know if it's road legal in Cali. The car is otherwise stock except for the flex fuel kits I have in mind. Might add a Borla Catback and catch can which should not affect the test anyways.

Also, what kind of WHP can I expect for a NA stock car with a reliable tune? (Maybe upgrade injector oil cooler and all those fun stuff if necessary)

As long as you don't have to turn off codes or have readiness checks incomplete that it should be fine. I think a stock car will make 30 whp over stock on e85 tune.

What exactly do you mean by "turn off codes" and "readiness checks"

If you just change the tune to run on e85 then nothing will cause a problem with check engine lights or readiness codes. There are certain changes that can be made that will keep you from passing an OBD2 emissions check. I would consult your tuner. Try James Martin in Florida you can find him on the enthusiast Facebook page.

If you don't pop a check engine light, you will pass.

CA does not do a sniffer test anymore. Just OBD and visual.

You dont actually need a fle fuel kit to run E85, you can do it by simply flashing an e85 tune and putting e85 in tank on a completly stock car. Then you cou
d just flash back to petrol tune and fill with petrol prior to you require checks.

read links below basic tune guide would be a good start

then e85 on a stock car, you can do it with ecutek OFT or other tuning devices without flex fuel kit just need to be carefull not to fill with wrong fuel.

e85 on stock car

http://www.ft86club.com/forums/showthread.php?t=67310

E85 tune will cause the check engine light pops up? Or is it some specific settings in the tune? Also, does this mean that I don't even have to keep the stock tune as one of the maps just for inspection purpose?

E85 tune will not cause check engine light (as long as you run E85 fuel).

If for example if you purchased an Openflash Tablet you get the tunes for petrol & E85 for stock cars and cars with aftermarket catless headers.

The device stores your stock ECU calibration (tune) and you can also save the tune file to your computer. It allows you to flash the tune of your choice or your stock tune back to your car in about 5 minutes. About as difficult as using a phone.

Just to add on to what Steve was saying, prior to your smog you will have to drive around atleast a week or two on your stock tune with premium gasoline, the smog techs can fail you for not having enough history info on the ecu. I remember I changed the battery on my civic and went to get it smoged, the technician said you don't have enough history on the ECU he let me slide and told me to drive it around for a little bit then come back after a week.

Have you ever got pulled over by California cops while running non-stock tune? Would they ever notice?

No they won't notice at all, unless you have an exhaust then they'll send you to a state ref, it's CHP you want to watch out for. I have seen them do a checkpoint to randomly test for smog here in San Bernardino County. They throw your car on what looks like a portable dyno and run it but it's very rare. If you have an OFT it should be no problem because you can always flash back to stock, that is why I bought the OFT because it gives you the opportunity to go back to stock when needed. So if they ever do one of those random smog things pull over and reflash and if they ask tell them you changed batteries. If anything happens to your ecu Shiv is good at getting back at you and @steve99 is always willing to Take a look at your maps.

Exhaust? I was actually planning on a Borla catback, I thought all Catbacks are all legal? As for the OFT, do you have time to reflash to stock when you see the random tests?

Technically any modification to an exhaust with the exception of TRD is illegal, OFT takes 5 mins to flash just pull over prior to approaching the check point, I totally get what your trying to do. Your trying to be low key with the law flying under the radar but the fact of the matter is... You gotta pay to play... Hang on to your stock parts if an issue arises then you can always bolt back on your stock parts. It really depends on the cop too if they want to pop you for mods here are a few things to remember.

1) Don't drive like an idiot
2) Don't race people
3) Don't rev your engine for the attention
4) You have to pay to play
5) Your going to go against everything I just listed
6) Most Importantly, DON'T KILL ANYONE!

Thanks man. This is pretty helpful.