A) Not much. A chip will advance the timing and air/fuel mixture; however there will only be a slight increase in hp/tq mainly due the fact the stock ECU is already programmed to produce close to optimal performance.
A) Depends, if your malfunction indicator lamp shows up (check engine light), this is due to your O2 sensor telling the computer that more emissions are being produced. An after market chip can be programmed to fix this, however you can also buy MIL eliminators to fake the ECU to shut off the MIL.
A) The timing will have to be changed in order to gain maximum performance. Nitrous tends to make the engine run lean which can hinder performance on spray and possibly damage your engine. A chip can reprogram the timing more advanced to produce the optimal performance however you can also buy a mechanical timing adjuster.
A) No, a timing adjuster only performs as the name implies it adjusts timing. If you add a super charger, turbo or cam, you will need to adjust your air/fuel mixture also, and a T/A won’t do it. A chip also reprograms the ECU to account for many other modifications.
A) Absolutely not. The only thing that will void your warrantee is if the chip causes specific damage to the warrantee item in question.
A) No, I would be surprised if
you gained 5% on a stock vehicle, although 10-15% sounds about right on a
supercharged or turbo vehicle.