It's when all the boost gets to the inlet then the ECU cuts fuelling to protect the engine, it can be the result of failed wastegate mdulator or stuck wastegate... see this
http://www.discovery2.co.uk/wastegate.html ... in the 3'rd picture see the pipe pointed as "to metal intercooler..." take a longer piece of pipe and connect the intercooler side with the wastegate or join it somehow with the one from the right which goes to the wastegate...if after that the symptom is gone replace the modulator... meanwhile make sure that the mechanical wastegate is not stuck closed... follow the video untill the end ... also
if it's Eu3 engine unplug the MAF for a drive test as well