Steady State

In Steady state cinndition what speed should i normay use? as in the street I may be cruising at 40 Km/h but on a Hwy i may be cruising between 100 or 120 Km/h.

Thanks in advance

Steady state refers to any operating condition of the engine where the load and engine speed aren't changing. That can be at idle, or a cruise condition in normal road use. The road speed depends upon the current gear ratio, and other than changing the load has no relevance to the engine tuning. On a chassis dyno with load control, you can typically use whatever gear is convenient or works well with the dyno.

As David said, it's a term used for when one, or more, variables are held at a specific value. Usually this is rpm/speed which required a braked* dyno' that can vary the load to match the changes in the power/torque applied to it. It's a very useful tuning method as responses to small changes can be immediately seen. For example, you may wish to check the fuel and ignition at 5k rpm, if the dyno' is set to hold that rpm, it will stay at that rpm as long as the ngine has enough power to overcome the drivetrain resistance to reach that rpm - so by using a series of throttle openings (a mechanical stop or electronic setting for the desired map points) the engine can be mapped for the best torque across that rpm point. Another way of doing it would be to set the throttle for the TPS point to be mapped (more to speed up the process where a mechanical stop is required), then map to the various rpm points in turn.

For cruising, as you suggest, you're going to be on a light throttle opening, and depending on how the vehicle is equiped with specific focus on a fuel consumption readout, you can try fine tuning ignition and fuelling for that road speed (cruise control helps) for the minimum l/100km.