Have you done a compression test on all cylinders to determine the health of the engine. A misfiring cylinder will smooth out and be masked if you run the rpm high enough. Low compression in one cylinder could be the cause of the problem and racing the engine just mask the problem.

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2006 Infiniti G35
2001 BMW 3.0I E53 X5 Build date 08/2000 SOLD
Lotus Europa 1970 Destroyed by fire
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