29CC, 29CD despite new plugs and coil pack

[AussieXer]

I have an annoying hesitation/faltering when I accelerate from rest or from a slow speed. When cold it is accompanied by a flashing engine light which usually goes off after flashing 3 to 8 times. Other than that the car seems to run fine. My Foxwell scanner shows two relevant codes when this occurs: "29CC/not present, DME Combustion misfires several cylinders" and "29CD/not present, DME Combustion misfires cylinder 1". These faults reoccur after I clear them. I have replaced all the plugs and today replaced the coil pack on cylinder 1 but it is still happening. My local mechanic says he thought it could be an air leak. Any suggestions would be appreciated.