The BMW X5M F95  is already a high-performance V8 powerhouse straight from the factory, powered by the S63B44T4 4.4L Hot-V twin-turbo engine . But with the VAITRIX Stage 2 tune , your X5M can achieve full V8 potential across every rev range . Why Upgrade to VAITRIX Stage 2? While the factory X5M delivers strong acceleration, the VAITRIX Stage 2 tune  improves: Low rev torque:  instant throttle response Mid rev acceleration:  thicker, smoother power delivery High rev extension