Audi has revealed a special edition version of its RS4 Avant to celebrate the estate car’s 25th anniversary. The RS4 Avant Edition 25 Years will come with increased power over the standard car with an extra 19 hp meaning that the 2.9-litre TFSI V6 biturbo will produce 463 hp and have a maximum torque figure of 600Nm. The 0-100 km/h time is about half a second quicker than it was before at 3.9-4.1 seconds and the car has a top speed of 290 km/h. The new model comes with RS Sports Suspension Pro, which is a manually adjustable coilover suspension setup which gives a 10 mm lower ride height. In a…