measure the width of your current seats and measure the width of those seats
you will have an idea of how they will fit in, corbeau has direct sliders for the seats and our cars so you wont need to worry about that
Also A4's come in wide and narrow sizes. My friend has the wides in his 02 GT and they BARELY fit. They rub on his door panels under hard turning.. I would think the narrow ones should fit a bit better. Either way, I'm sure you'll be fine. Corbeau carrys the tracks as well... they retail for $79ish a side