Max Bobnar, an authorized Automobili Lamborghini SpA dealer for Switzerland had his personal Countach LP5000 S modified by Franz Albert, an Austria based engineer who installed two small turbo's on the 5.0 Liter V-12 engine.
These turbo pumped up the horsepower to a healthy 520 Bhp at 6500 rpm, with this engine installed the Countach LP5000 S Twin Turbo managed to reach 100 Km/u (60 Mph) in 4.8 seconds, instead of 5.9 seconds for a 'standard' 5-Liter unit. Top speed for this special Countach isn't recorded, but Max Bobnar drove it at a sustained speed of 290 Km/h (180 Mph) with still room for more, he didn't push it all the way because he didn't know if the standard suspension could cope with speeds above 300 Km/h.
The current whereabouts of this car are unknown to me, if anyone has any idea, please let me know.
There seems to be another turbo charged Countach out there too, read about it on Teamspeed.com