the S4 is the mid-level performance version of the Audi A4 saloon. Swapping between twin-turbocharged, supercharged V6 and even a naturally aspirated V8 engine in times gone by, the B9 S4 returned ...

and the outgoing Audi S4. Audi “Quattro ultra only comes on the B10 A5, not the S5. The B10 S5 employs the same standard quattro with sport diff as today’s B9 S5 with the S sport package.

Buckle up, gearheads, because we're diving deep into the heart of Audi's B9 generation A4/S4—a tuner's paradise that Canadian Auto Performance knows all too well. This platform isn't just ...