Anyone can make good power in perfect conditions. It takes real tuning talent to make it happen on regular 91 octane Arizona pump gas in the middle of summer heat soak. This Mercedes-AMG GT63 rolled onto our dyno and put down 711.9 HP and 744.6 lb-ft to all four wheels, and that's the real test of a quality tune: how it performs when conditions aren't ideal. That's what g ood calibration looks like: a Weistec W2 ECU and transmission tune doing its job even when the fuel and t

Kline Innovation builds some of the most beautifully fabricated equal-length turbo manifolds — or headers —, and Goodspeed Performance is proud to be the direct Kline Innovation importer in Arizona. The moment you see a set in person, the quality is obvious: hand-welded stainless, mandrel-bent runners, and finish work that looks like sculpture. But it's more than looks. Kline tunes each runner to a precise length so the individual exhaust pulses arrive in sequence, which inc