Found this
http://www.splparts.com/doc/tech/EBC.htm
It explains how the controllers work. It talks about Duty Cycle.. here is a quote..
I do not know enough about this subject to say that this is 100% correct, use it as a guide only. do some google searching on the subject and allways start with low numbers.
Here is the quote -
Most boost controllers accomplish this by figuring out what percentage (or ratio) of the time the solenoid would connect the wastegate to the atmosphere vs. connecting the wastegate to the intake. This ratio is often known as the DUTY CYCLE, the duty cycle is directly related to the boost level.
How to set up an electronic boost controller in manual mode
In manual mode, there are two numbers that has to be determined: DUTY CYCLE (sometimes also labelled as SET) and GAIN. The optimal gain number always depends on the boost level you want to run, if you are running very high boost, then you want the wastegate held closed for a longer time since it takes a longer time to reach the higher boost. So the first step is to determine the duty cycle:
1. Start off with a low DUTY CYCLE and GAIN setting.
2. In a higher gear (3rd or 4th), run the car to see what boost level the duty cycle corresponds to by watching what steady/stable boost level is reached. Increment the DUTY CYCLE with each run till you reach the boost level you want. Fine tune as necessary. If you notice boost spikes, then you have set the gain too high, you do not want spikes at this point since that makes it more difficult to see the steady/stable boost level.
The reason why you should use the higher gears is because in the low gears, things can happen too fast to figure out what the steady/stable boost level is. Now that you have figured out the duty cycle that will give you the boost level you want, the next thing to do is to work out the gain:
3. Make runs in lower gear (1st or 2nd), increment gain with each run till you see boost spikes. Then fine tune it till there is little or no boost spike. This is your optimum gain setting for that boost level.
The reason why you should use the lower gear now is because boost builds much quicker in the lower gears, so there is a higher tendency to boost spike.
When setting your boost controller, always have a passenger set the controller and watch the boost gauge for you, the driver should keep his eyes on the road!
Common problem
Sometimes if the gain is set too high, it may appear to have the same effect as the duty cycle. If you notice (especially in the higher gears) that you initially hit the boost level you want, but then it starts tapering off, then you might have set the gain too high and the duty cycle is not set correctly. Or you might have a boost leak...
