The stock intercooler pump goes quick on these cars, mine went at 34,000. Intermittent booost is the main symptom. Someone else did a great write up of their issues, somewhere on this forum. They realized it cuts out about every two minutes, as the supercharger gets too warm. Then, the boost comes back once it is cooled, and this cycle repeats. The first time mine lost boost, the car did what you described: sudden boost without me changing pressure on the accelerator and then no boost while pressing the accelerator.

My personal experience with losing boost and solving it by replacing the intercooler pump:
It took about 20 minutes, most of that was getting the plastic out of the front right fender well. I bought the Bosch, I think, pump from needswings. The only specialty tool requires a torx socket, or however you spell that. Then, afterward, I had the same problem...because my system has an aftermarket separator between the intercooler pump lines and the radiator lines. I had to re-establish flow from the main reservoir to the intercooler by opening two shut-off valves attached to the radiator/intercooler lines.