A weak spark has fooled many a technician. It is the first place I start as I was fooled once, and only once!! After I have ruled out the ignition system as a possible problem then I will pursue the injection system as a possible cause.

If you feel you are having a fuel injection problem than what is helpful is to post any pressure readings that you may have taken from the car. As I did not see any hint of that being performed I was merely suggesting a path to eliminate possible causes which ultimately save you time, as well as money.