completed six prototypes that were further mechanically assembled by Alfa Romeo. Two of those protypes were presented at the Frankfurt Motor Show. 1,973 berlinas and 1,678 Sportwagons were built until the GTA production stopped in October 2005, as the V6 engine as unable to meet emissions regulations and due to the 156 being replaced by the 159. The GTA was sold in limited numbers, with right-hand drive vehicles holding a premium over left-hand drive vehicles due to their rarity. The very first GTA was sold via online auction, from 13 to 23 September, the duration of the Frankfurt Motor Show. Winning bid was €48,691.26, which was donated to "Telethon" charity fund. The 3.2-litre Bussone V6 engine (The big Busso, so-called after legendary Alfa Romeo engineer Giuseppe Busso). This engine is praised universally for its sound and revving capabilities. This was the largest iteration of the engine built by Alfa Romeo. The engine has a bore and a stroke, displacing at . It was rated at and of torque. Overall, the car weighed more than the standard V6 156. The GTA variants shared a common interior with post-facelift 156 variants. The doors, boot lid and bonnet were also shared. All else was unique to the GTA, with the engine specifically made by Fiat and Maserati Research Centres. The GTA did not receive the Giugiaro designed facelift introduced on the 156 in 2003, but continued with the acclaimed Walter de Silva design to the very end of production. The steering was also made faster, only 1.7 turns from lock to lock compared to 2.1 in normal models. The GTA had also larger brakes (Brembo), at front discs and rear . The front discs were later upgraded to to cope with the performance potential. 156 Sportwagon Q4 In 2004 Sportwagon Q4, an all-wheel drive version of the Sportwagon was launched in some markets. The Q4 (short for Quadrifoglio 4) system used three differentials, the central one being of the Torsen C limited slip type; it added about to the vehicle weight. Graziano Trasmissioni, the Turin-based transmission specialist, developed this system. A raised ride height meant the Sportwagon Q4's was tall. Other than the ride height, special 5-spoke 17-inch wheels and a "Q4" badge on the tail set the Sportwagon Q4 apart from the front-wheel drive 156 versions. The Sportwagon Q4 was only available on LHD markets, with no RHD models being built or