Fair play switchblade but i dont see why you would need two forms of adjusting boost (actuator and bleed valve) unless you cant be arsed to spend all of 20 mins it takes to adjust the actuator and so use a bleed valve instead, but then you may as well not have the -31!!
All it will do is facilitate rapid boost adjustment, great if your a tuner in a rush to get the next job on the rollers and this one out the door!
But like everyone says if its set correctly and left alone there is nothing wrong with it. I dont have anything against them they do there job perfectly, but if it were me i'd just take the time to set the boost using the actuator.