I'd bring it in and have them read the codes. I had this once, diagnosed as engine not making full boost.
They re-set the codes and the issue has not re-occurred so far (~4 months). It never was clear exactly what happened.
http://www.1addicts.com/forums/showthread.php?t=773300
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1M, GT4, 1969 Porsche 911 w/ 997 GT3 Cup Motor (435hp & 2,100 lbs)