Switzer Performance Innovations (SPI) in Oberlin, Ohio, is different from most aftermarket firms because it is not just a tuner but an intricate research and development lab for high-end performance products. I was invited to the Nelson Ledges Raceway in Ohio to test-drive SPI’s latest projects: the Porsche 997 GT2 and Nissan GT-R. Initial laps were treated as a warm-up both for the machines and me, but my pace quickened as I began to rein in all 800 hp from these retuned sports cars.