Before you get attacked and scolded about not using the search function, let me tell you in a polite and pleasant fashion that your problem is the Intercooler Pump. It needs to be replaced and then everything will go back to normal.

Basically the intercooler pump either goes out entirely or starts working intermittently, and this causes the coolant to sit stagnant in the intercooler heat exchanger. The air going through your intake is then heated by the supercharger, and causes the Intake Air Temperature sensor to send an overheat code to the computer. That code disengages the supercharger and pulls timing, and makes other adjustments. This causes the loss of power you are describing.

The first thing your dealer is going to want to replace is that Intake Air Temperature sensor. That's fine, you can let them go ahead and replace it...but then insist that they drive it hard for at least 20 minutes to see that in fact, that didn't fix the problem, so they can then move on to the intercooler pump which IS the problem. Took my dealer 3 tries, to believe me and actually get the part and replace it. If you can do it in less than 3 visits, you're in real good shape!