I had a similar problem where when driven hard (full load/high rpm) the engine would cut in and out. Seemed to get worse when hot. I would let the car cool off and it would be fine for a while.
It turned out to be corroded PTU connections. My theory is that at low rpm the connections were good enough, but at high rpm when all those connections are firing faster it just couldn't handle the higher electrical loads. I'm not sure if that theory is sound, but I know after I clean those connectors it never happened again.
Like the boost leak check, it's an easy/free first thing to try.
Good luck.
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90 300zx TT 13.285@106.08 (old stock turbo set up) 94 Camaro Z28 13.751@101.83 03 WRX 13.973@94.88 02 Mazda MPV; four kids and a wife don't fit in the Z. 90 240sx (sold) 16.9@87
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16:43:16 09/17/12
