How to Prepare for a Dyno Tune

TECH

Dyno tuning is one of the safest and easiest ways to get more power out of your car. You can bolt on parts all day long, but without making the necessary changes in the ECU, not much will come of it.  In fact, you might be worse off than if you didn't put those parts on.  But strap that car to the rollers for a few hours with an experienced tuner behind the wheel and watch as it suddenly comes alive.
As easy as it sounds, it isn’t as simple as just strapping the car down for a couple full throttle ramp runs. There is quite a lot that goes into dyno tuning a car and it is your responsibility to make sure your car is capable of safely completing a dyno tuning session.

A dynamometer or dyno is designed to simulate real world driving in a safe and consistent environment. The dyno also can monitor torque and calculate horsepower based off torque and rpm so it becomes a useful tool for tuners to use to optimize a car's performance.
But since a car can’t be fully optimized in one or two passes on the dyno, you will need to make sure that your car is up to the task of repeated pulls, and depending on the work being done, anywhere from 2 to 4 hours of dyno time. Below are some things to check before bringing your car to the dyno to ensure it is in optimal condition for the testing that will come.
 
Boost/Vacuum Leaks
Boost leaks will be found in any piping or part that is between the turbocharger's compressor outlet and the head of the engine. When you have a boost leak on a Mass Airflow (MAF) Sensor based car, you are losing air that has been measured already and this will not only cost you power due to lack of boost pressure being able to be maintained, but it can also cause the car to run dangerously rich.  If your ECU is setup properly, the engine might still run safely even with a small boost leak but it will not have the power and efficiency it should.
A leak between the compressor outlet and the throttle body will cause the car to run rich all the time as it will always be losing metered air. If the leak is in the intake manifold, it will pull in unmetered air at idle and in part throttle conditions where there is a high amount of vacuum in the intake manifold. This will cause the car to run lean at part throttle but rich at wide open throttle. With a boost or vacuum leak, the car will be impossible to calibrate properly.
If you are not sure whether or not you have a boost or vacuum leak and don't feel comfortable doing the test yourself, you should take your car to a shop and have a leak test performed. This will ensure a successful dyno day.  Many dyno shops even require that you allow them to test your car before they strap it to the dyno to prevent further wasted time.
Leaks in the Intake
If you have a pre-turbo leak, the vacuum created by the turbo will constantly be sucking in unmetered air (in a MAF based car) and this will present as a persistent lean condition at both wide open throttle and part throttle/cruise. If your car has an intake leak, it will be impossible to calibrate it properly. 
Exhaust System Leaks
Exhaust system leaks can cause back pressure and scavenging issues on a naturally aspirated car and can cause slow spool and lean readings on a turbocharged car. If a leak is persistent in your exhaust anywhere in the manifold or before the O2 sensor, there could be calibration problems that can halt tuning and cost you a lot of unnecessary money and time.
You can check for signs of a leak by inspecting for carbon build up around flanges. A preventative measure here is replacing gaskets when you change out parts like the exhaust manifold, downpipe, or turbo. 
Mechanical Operation
Before going to the dyno it's important to make sure that your car is operating as it should mechanically. If you have aftermarket catch…