Remove the black box and have the dealer fix the car. And I agree with darkhorse, there could be something wrong with the black box, even if tehre is no red flashing light.
You keep mentioning that you have checked the wiring, bu you need to check all the hoses and tubes, etc., in the boost system.
Your car is under warranty, right? I insist that the dealership should fix this. However, since they know you put a black box in it (why on earth would you ever let your dealer know this, I don't know), let's just hope they don't decide to void your arranty.
Best of luck.
Please let us know how things work out.