how can i fix my vectra?

i have a 1.8 vectra sri and a few wks ago the engine management light came on and the car started spluttering and had no power at all. i got a new ecu and it sorted the problem out 4 about 3 wks an now its started spluttering again an the power as gone but the engine managment light hasnt come on ppl av said it could be the injectors could this b true. sometimes itl splutter till u get to 2500rpm and it seems to av power when it gets past that.