Why would you need four boost settings??
I have 2, one for all my driving 16 psi, and one for wet days 7 psi. This is basically an effort to stop wheel spin, a softer take off or turbo wind up.
You will drive on your maximum boost setting [but NOT maximum boost] 90% of the time. There is absolutely no advantage in driving on a lower setting, fuel economy etc isn't improved. Look at it this way, you have 18 psi as your normal setting, you are driving down the road at 120km/h, your still only using say 3 to 5 psi of boost [actually you'd be lucky to be boosting at all], the point is you are not using 18 psi. The only time you are using 18 psi is when you flatten it and hold it flat until boost peaks ie 20 seconds or more. And the only time you will do this is when you want or need to. ie overtaking a couple of b double semi's, showing off at the lights, track days. This is why you leave your boost on the higher setting, you never know when you need the power, and playing around with buttons may be too late!! Added to this, nearly all good boost controllers have a scramble setting for 10 seconds. You set this parameter yourself. What you do is nominate a peak setting that your motor can handle for 10 secs with no problems, say 22 psi. So you are overtaking the B doubles and you go WOT, your boost will actually try to go to 22 psi for the first 10 seconds then it will settle back to your normal setting of 18 psi. This will give you a little extra oomph as a first up hit. I'm not sure [i can check if needed, I did know more but have forgotten, you do all this stuff and set up your evc and then begin forgetting it] but I believe that this scramble setting may only work in the top gears, not in 1st or 2nd. This then ensures that your motor actually has a load on it for some protection against overboosting/reving.
I hope this helps.