hi there just bought a audi a4 avant 1.8t stuttering line quattro. has full audi service history and a clean mot just done with no advisories. also has had the cam belt and water pump changed at 75000 . the car has done 115000. every thing on the car seems fine apart from when I accelerate and then seem to missfire a bit between 3 and 5000 rpm. but if I boot it from first and keep my foot down through the gears it doesn't do it. pls help or advise if anyone can pls . any help much appreciated. thanks.