Hi, I own a BA 2004 XR6 Turbo sedan (automatic). What I have noticed recently is when I start to accelerate extremely quickly (ie kick down on accelerator), say from stand still or just cruising along at 40 km/hr, when car reaches around 85 km/hr at about 4,000 RPM to 4,500 RPM, the engine starts to run very rough and I can't continue with the acceleration to go beyond 100 km/hr. I can continue driving, however, engine runs very roughly and then have to switch off engine to clear the rough effect from engine. After switching engine off and turning back on, engine runs normal and smooth. If I avoid these kind of kickdowns, I can easily achieve higher speeds (eg 120km/hr and above) and engine runs smoothly. Can anyone suggest what could be at fault during 'kickdown' and what I should do? Cheers, Bill.