Would it not make more sense to get a proper diagnostic check done, i.e. live data tests of the various sensors and actuators, NOT just a basic coderead which many garages claim to be a 'diagnostic'?
There are lots of independents offering this nowadays, a few 'phone calls could save you a lot of time, money and grief.
Although the AFM is a common failure, there are too many possibilities to make random part replacement economic or practical.
espley, April 2009