Acceleration/driving

hi my car is a subaru impreza 2ltr auto estate it starts fine every time but when you go to pull away it feels like there's nothing there and will only pull away very slowly even if you have your foot to the floor. if you hold your foot down it does pick up and accelerate after a few seconds. the problem becomes a bit better when the engine has warmed up but is still there. also the check engine light comes on intermitantly. i have tried three different air flow meters with no difference and have just changed the lambda sensor this too has made no difference. any ideas people i am getting rather annoyed with it! cheers