My Saab 9-3's ECU learning makes a huge effect. It cuts fuel off much more aggresively and also limits boost pressure in lower rpms once it realizes that most of my driving is city. I think this is to lower fuel consumption and emissions. Disconnecting the battery or the right fuse for just a moment really changes the nature of the car.
If you feel you like it this way, try to find the correct fuse (should be written somewhere in user manual) and you can reset it at will then without disconnecting battery and loosing stuff like time settings, etc. A lot of Saab guys do it like this - some even have automatic ECU fuse "disconnecter" so that the fuse gets disconnected whenever the car is turned off.
Note that the Saabs won't pass emissions in this "factory defaults" mode - the car needs to relearn to be able to do so. On Saabs, it takes ~100 miles or so I heard. Not sure if the Kizashi would pass or not.
Battery died but something interesting happened
So basically you clean booting the computer with every startup. Who wrote the ECU code, Microsoft and it's running under Windows XP? 
2011 Kizashi SLS CVT (silver)
2005 Honda Odyssey
Priors:
2009 Suzuki SX4 Cross AWD 5-speed Tech package (vapor metallic blue)
2005 Honda Odyssey
Priors:
2009 Suzuki SX4 Cross AWD 5-speed Tech package (vapor metallic blue)
Well I'm too lazy to do it so I don't (unless before a long trip and want to have more fun).
The ECU is able to re-learn both ways (become more passive or more aggressive), but it almost always ends up in the economic mode, which works well if the driving style is consistent with the adjustment.
I wouldn't be surprised if they did this to be able to declare lower fuel consumption = less emissions = lower price of car (due to lower emissions tax for manufacturer).
It's the same thing the Kizashi does with CVT - dropping the rpm as soon as possible and lugging around to save fuel unless you stomp the gas.
The ECU is able to re-learn both ways (become more passive or more aggressive), but it almost always ends up in the economic mode, which works well if the driving style is consistent with the adjustment.
I wouldn't be surprised if they did this to be able to declare lower fuel consumption = less emissions = lower price of car (due to lower emissions tax for manufacturer).
It's the same thing the Kizashi does with CVT - dropping the rpm as soon as possible and lugging around to save fuel unless you stomp the gas.