Splutters and stalls on acceleration

My car is the Grand Scenic model. Firstly, 'Check Injection' came on the dash with lumpy acceleration (splutters and stalls) and limited to 3000 rpm.

Have replaced glow plugs, and mass air flow sensor and same symptoms (although much much worse when mass air flow sensor is plugged in, so have to have it unplugged to get anywhere).

Have taken off the EGR valve and cleaned it up and banged it a few times. Car worked a lot better to start with and now back to initial symptoms. Have to keep the foot down (high revs) and low gear in order to minimize the lumpiness and stalls.

Tried unplugging EGR, but no change. Cannot get to TDC sensor myself as battery clamp nut just keeps turning.

Any ideas?