As recently as 2002, Audi had a new A4 on its hands. With such a comprehensive round of innovations at the time - new look, new engines, new Continuously Variable Transmission, new convertible - you'd think its expiration date would be set far into the future. But if it's surprising to see Audi executing a mid-life update that nearly qualifies for a new generation after three years, well, maybe it shouldn't be. When you've got Infiniti and Acura on your tail, you gotta act fast.2005's changes start with the visual. Fresh taillights combine with Audi's gigantic I'm-going-to-eat-you grille to ensure that you'll now confuse the A4 with other Audis from the front instead of the back. The fun went from seeing an A4 come to seeing it go.And there is more fun in going. 2005 sees the most aggressive year-over-year engine boosts, with the turbocharged 1.8-liter 4 becoming a 2.0 and the 2.8-liter V6 increasing to 3.1. It gets a lot more technical than that, however, and in addition to more go, the A4 gets more stop and steer. The once-vast model lineup has decreased in diversity but still stands with five different drivetrain combinations; my experience reflects one of them.