It is no different today then it had been for many decades before electronic engine management existed

We had timing lights and dwell meters, different jets for the carb and different springs to change what the over all timing would be.

Today it is no different as how much fuel, air and timing a engine needs for best performance.

One difference we do have today is EPA sticking their noise in our tailpipes and forcing less performance by assuring non wide open throttle conditions are always lean which is a AFR around 14.7:1 or just about 15 parts of air for every 1 part of fuel.

We add one more issue and that is the nameplates to reduce the amount they have to pay out for warranty work is have the engine management prevent maximum ability of engine to produce more torque then the drivetrain can support or to put out enough torque to cause rear tires to loose traction and car getting out of control.

Since I worked at the GM Tech center I know they go by the 80% rule meaning they attempt to limit only 80% of the engines ability outbound to assure 100,000 plus miles for engine.

Lastly GM has to build one common engine control calibration that assures no matter who is driving the car, how they tend to drive, weather and gas conditions that the car will function fairly well so their tune is "generic" and not calibrated for best performance.
Even where the car is in elevation or change of elevation can effect performance and no ONE stock calibration can make chamges for all those conditions and assure best performance even if the car is 100% stock.

Add all the good and bad mods people buy today takes that stock calibration and the outcome is even worse to performance.

To clean all these changes up is the purpose of our custom tuning.
Simple answer to those asking " what would a stock car gain with a tune ? "

Normally about 30 HP and much better overall torque throughout the RPM range.

Other changes in a tune give better control of what happens if there is engine knock. GM allows as much as -15 degrees of timing to be taken out and if knock happens multi times in a row it switches to a low octane timing table and stays that way until gas has been added to the tank so until that is done the engine functions in a less performance mode
Proper tuning prevents so much timing to be pulled and with correct tuning methods prevents most knock from happening in the first place so the timing is always at best case for performance.

Same goes for tuning misfire function and what is called "torque management". As more mods are added to the engine the more torque engine produces which if not tuned then any time engine outputs higher torque then what GM's tune is will force the engine management to react, force lower torque output by controlling timing, fuel flow and takes over the drive by wire to control how much the butterfly of throttle body is to limit air into the engine.

Custom tuning is just that, it allows not only engine to output 80% of it's ability but also marry the mods installed so they work best with total engine design.

Custom tuning not only increases performance but also can gain gas mileage, allow engine to run cleaner and cooler, labors less, functions better from time engine is started to going WOT.
Tuning also allows custom setting how a automatic transmission functions and split tuning allows engine to function one way for part throttle and totally different when performance is wanted at higher engine loads and RPMs.

Tuning then allows true custom setting for each drivers driving habits, types of fuels used, what mods where installed and how much output the engine can really produce.

Once tuned and unless other mods are done the tune is forever and does not change.
Only way to lose the tune is by replacing the PCM or allowing someone to overwrite the tuned calibration in the PCM with another calibration

A well thought out custom tune will allow engine to function better then stock calibration so engine will work long term very well and still put out good performance.

Due to sevveral cheap costing tuning products being on the market today any one buying such a tool and claiming to be a tuner has produced some very bad running cars that can even harm or destroy the power and drive trains.
There are no schools to learn this it is a black magic that only those of us who solely tune for a business for many years tuning 1,000nds of cars truely know how to do true custom tunes to allow the performance but also assure engine is functioning safely.

We have tuned cars 5 years ago and recent analyzing of them show the tune is still best calbrated to the engine and performance is good yet has passed EPA smog tests all those years.

Team ZR-1
True Custom Performance Tuning