What I suspect you're doing wrong is holding the brake and throttle for too long. This methodology works only if you perform as an upswing method where you're not holding revs.
Left foot on the brake firm, right foot engages the throttle. As soon as revs build to around 2k, release the brake pedal and floor the throttle. You cannot sit holding revs, it will make the car limp off the line (happened to me once)
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