Rep added to chris and also some sort of a guide i found.(reference to MS users but gives some good points tho)
Preparing to take your car to be tuned
You or your installer should insure of the following things before taking the car to be tuned. Keep in mind that dyno time is not very affordable diagnostic time, you don't want to be figuring out problems on the dyno. The operator is more than likely going to have to charge you shop rates even if the dyno isn't operating as you're still essentially using the dyno and they can't have any other cars on it until your car is off.
Make sure your install is complete
You car should be running perfectly, just not tuned yet. What does that mean? It doesn't mean you can drive your car at all...
It does means that the car should be starting and idling reliably at all different coolant temperatures that will be encountered.
It means all sensors are reading properly in the tuning software.
That you've properly calibrated the coolant and IAT sensors if need be.
Your TPS sensor is calibrated.
That you don't have any strange ignition misses, etc. If possible, do enough research on tuning the car yourself, and with the help of a wideband if available, free rev the engine a bit and keep the AFR in the safe zone by dialing it in (while free revving, for the purposes of this test, 14:1 is a good target AFR), you're really just looking to see if the engine revs fairly well with no load on it to help ensure the EMS install is complete and free of issues you need to work out.
Make sure you've properly figured out your dwell settings as per the MegaManual-- too little dwell can cause misfire, too much can burn things up. The tuner is likely to guess at this number if he thinks it needs to be changed, you have the information you need in the MegaManual though-- you or your installer should have this right before the tuning session.
Forced induction cars-- Your IAT sensor MUST be AFTER the compressor, and AFTER the intercooler. Preferably just before the throttle body inlet. It needs to measure the actual actual air temp that's entering the intake manifold, hence the name intake air temp (IAT) or manifold air temp (MAT). If you are measuring ambient air temp just after the filter, then heating the air with a compressor (SC or turbo) then maybe you cool it with an intercooler, who knows what temp that air will be when it enters the intake? The ECU surely doesn't, and your fueling calculations will suffer badly.
If you have a wideband, make sure it's reading properly (installed and calibrated properly), and preferably have it's output piped into the MS where it can be datalogged. Have MegaLogViewer loaded on your laptop for quick log viewing.
Your cooling system should be adequate-- much of the time spent on a dyno is spent waiting for a car to cool down, the better your car manages heat, the faster your tuning session will go.
Make sure your car is well maintained
The spark plugs are in great condition, new is even better, and properly gapped.
NOTE: If you've installed forced induction on a stock n/a car, you should got with a 'colder' plug, at least one step colder. Also it's likely you will want to gap the plug a few thousands less than stock. For example if stock is .035 maybe go to .028, if needed later during tuning (misfires under boost) you could drop the gap a tiny bit more. Check the plugs after driving the car a bit- if the plugs are too cold they'll foul quickly, if they're too hot (as stock n/a plugs may be with forced induction) then you could have pre-ignition/detonation. Usually I start with 2 steps colder, then read the plugs, if they're reading dark even though I know my fuel mixture is right then I'll change to only one step colder than stock and that's usually fine.
Make sure the rest of your ignition system is in great condition-- wires, distributor cap, etc.
Make sure all fluids are fresh and topped off. Oil/coolant/etc.
Make sure you have your wheel lock keys if you're going to a hub dyno such as a DynaPack!!! If the tuner can't remove your wheels it's a no-go...
