with backfire, like most have said, comes down to luck for one thing cause there are no playback controls. the next method of shifting gears, I haven't tried that personally cause i use a DS3 and it just stick with automatic.
however, what i have found out over the week end is that if you take the photo from a distance and straight on at the car, it proves to be much more effective. I don't have the pictures on my computer right now to illustrate my point, but in words, it comes down to this:
say your car has backfire before it is entering turn 7 at the monza circuit (which was what happened in my senario on the ferrari challenge)
you have paused to take a picture, but instead of standing right next to the car within a 10m radius, go back approximately 150m back into the straight leading to the corner.
using the camera tools, full zoom right up to the car from where you are standing
the car might look out of focus, then use auto focus on the car
set the camera settings to what you desire, i used a 1/60 shutter speed, with F 8.0 or more. because you have auto focused on the car, lowering the F value will lead to the surrounding scenery to blur out, if you want a blurry scenery surrounding the car, higher for a more crisp and stationary picture.
take the picture and voila! although it must be said, i took the picture straight on from the back of the car which made it significantly more clear. when i attempted to take it from the side it would just screw up. will try and show this with some pictures soon.