How to fix a mis firing zafira? ?

Our 06 1.6petrol zafira has just had a new ecu fitted but now seems to losing all ignition electrics for a few seconds at a time at around 2 to3000 revs when driving. Speedo and rev counter needles flick down and battery light comes on momentarily before you blip the throttle to get it revving again. Some say it could be a fuel filter blocked but it seems too electrical. Any ideas? Thanks