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Your best bet is probably buying a jdm built motor or trial, but they are going to react much like a turboed motor at those displacements, without the torque. At the track you're never going to be dropping below 5k so lag will not be an issue. Of the turbo cars you've driven on the track, were they track/race cars, or street cars driven on the track. A turbo car built and designed for the track has very little downside when it comes to driving dynamics. Most racecars use turbos as power adders, not superchargers, for good reason. On the street you may have different requirements. Of the cars I've added turbos/superchargers to I've had far less issues with the turbos.