Ford Focus car and steering wheel shakes on acceleration

When accelerating at around 2000-3000revs the car and steering wheel shakes and the car struggles to accelerate. When the car gets to desired speed the shaking eases off when i take my foot of the accelarator. This is especially a problem when accelerating up hills or accelerating onto dual carriageways. There is also a funny smell from the engine when it does this. On a recent service it was picked up that the emmision breather hose was split causing rough running. I have had this replaced but the problems remains. Anybody got any ideas?