First, a word on warranties-understand that a tune makes a vehicle make more power.  This is outside of what the manufacturer often originally intends, and may alter some of their methods for emissions control and power output.  In simple words, you may break things.  Breaking things may or may not get covered by your warranty.  What you need to know directly is that GM looks for a checksum value on each file-if the stock file is there, regardless of any prior tuning, it shows up as untuned.  So if reflashed to stock, they'll never know.  Ford, on newer PCMs, has started a "flash counter".  It records the number of times the computer has been flashed as well as what tune is currently in.  So, if you have been tuned they'll know.  Whether they check or not, however, or care that it has been tuned, is on an individual case.  Know that if you do radical modifications, you should take responsibility and not expect to get warrantied if you're making twice the stock power level and you kill the transmission.  If your paint peels, expect that to still be warrantied as it's unrelated to any performance enhancements...unless you go really, really fast.

Now, let's face it-your vehicle wears out over time.  More to the point, things on the vehicle wear out over time.  That being the case, let's go over some things you need to know BEFORE you tune your vehicle.

First of all, a quick rundown on what tuning equipment does.  Your engine is like an airpump, and what tuning does is make sure there's just the right amount of fuel based on the amount of air the engine is pumping.  One of the things the wideband oxygen sensor will do is look for how much loose oxygen is present, indicating not enough fuel.  On the flip side, it will also look for how much excess fuel is present, indicating possibly too much fuel.

The wideband is extremely accurate at detecting oxygen or fuel.  However, it has no way of knowing WHERE that oxygen or fuel comes from, so wear items on your car that can introduce fuel or oxygen NOT from combustion will "trick" it.  Here's the rundown of what you need to have in good shape and why.

Exhaust leaks-a leak BEFORE the oxygen sensor will allow air to enter into the exhaust, which contains oxygen and no fuel, and thus make a sensor read that the mixture is lean (not enough fuel).  Regardless of how much fuel the computer adds, it will always want to add more.  Obviously this hurts power and fuel economy.

Fuel injectors/fuel system-since this system is directly responsible for the fuel, this system is also very important.  Leaking injectors, clogged injectors, and other problems will throw a tune off.  Think of this-if an injector is 10% clogged, and therefore only spraying 90% of the fuel it should, when tuned it it will compensate for that.  What happens if a few months later you add a fuel system cleaner and unclog it?  The injectors are now spraying 100% and the tune is 10% rich (too much fuel).  It is a good idea to run a fuel system cleaner and change the fuel filter on higher mileage vehicles before a tune to make sure the tune stays consistent.

Spark plugs/wires/ignition system-If the ignition system is not up to the challenge of burning the fuel, extra fuel gets dumped down the exhaust, causing the wideband to think it's a rich condition (too much fuel).

Stock oxygen sensors-stock oxygen sensors do much the same as the wideband, but only in a narrow, non-performance range.  However, the computer in the car uses them to make gradual adjustments, so if a sensor is bad, the computer may keep adding or subtracting fuel in order to get to what the sensor is saying is right.  Even the best tuned car will become out of tune this way.

Other sensors-there are many, many sensors that modern engines use.  They are all important.  Most notable are sensors such as the inlet air temperature sensor, mass airflow sensor, and manifold absolute pressure sensor.  These have a direct hand in the computer's prediction of how much fuel to spray.  There are also other sensors that could have effects.

Electrical/power issues-the computer in your car requires a certain amount of power to operate, and for the tuning software to communicate with it.  Anything under 11-11.5 volts, and writing to the computer can cause damage to it.  Of course this will be checked before a flash, but vehicles have come in that would drop from 12.5 volts to under 9 within 10-15 minutes due to electrical gremlins.  Greg's Tuning Operation is not responsible for computer damage on vehicles that rapidly drop voltage!

Greg's Tuning Operation is NOT responsible for any damage that results from a car not being properly maintained or in proper working order.  Further, if an issue arrises that is due to vehicle neglect, extra charges will apply for extra time spent.  A basic rule of thumb for normal maintenance is that if you have a "Service Engine Soon" (SES) light on for almost ANY reason, the vehicle needs maintenance before it needs tuned.  The exclusions to this are removing catalytic converters (which will throw an oxygen sensor code until tuned) or major  modifications such as heads/cam swaps or forced induction.  Also, if your vehicle requires a lot of jumpstarts, it may have electrical issues.  Minor ones can be worked around.

If you are unsure about the maintenance of your vehicle, contact GTO.  Another option, especially if you do have an "SES" light on, is to go to Auto Zone, O'Reilly's, or similar auto parts store, which will scan your car for free and let you know what the issue is.  GTO can likewise scan the computer.

The whole purpose of a computer tune is to make a car run better, but it's only one part of it.  Proper vehicle maintenance is a vital part of making a car run as intended.  Besides the items listed above, vehicles need to be in good general shape, with no safety issues such as bad brakes or bald tires.  The engine also needs to be mechanically sound-oil getting into the chamber can cause damage to wideband oxygen sensors, which are expensive.  Oil can also throw off the oxygen sensors.  And an engine that is on its last legs will not gain much from having a tune.

Now, a brighter side-performance modifications.  Some modifications will not have much effect on a tune-most will. While GTO does not mind charging to retune cars, it is advisable to be smart.  If you plan on adding something in the very near future, say a cold air intake next week, you're best off waiting to have your vehicle tuned for a week or two.  Such a modification would benefit greatly from having a complete tune, as it directly changes the amount of air getting into the engine, as well as the way the mass airlfow sensor will see the air coming in.  If, however, the modification is a few months away, you may wish to go ahead and tune the vehicle immediately, and then follow up with another tune.  Follow up tunes are less expensive, but money is money.  Muffler swaps are one example of a modification that *may* not require a retune to get the most out of them, but for most everything else you will want a retune to get the most out of your modification.

If there are any questions or concerns, feel free to contact Greg's Tuning Operation for advice.