Over the weekend my MK1 Ford Focus 2.0 Zetec has devoloped 2 issues.

It is hard to start from cold sometimes you have to give it a rev to get it tto fire up and sometimes sounds like its running on 3 but rev it and it clears, also at low revs, it is really jumpy and misfiring, anything about 2500 revs its fine but the lower the revs the more it kangaroos about, i was thinking fuel filter/spark plugs ? but unsure.

Also the steering when the wheel is centre, as in driving in a straight line, if you go to steer right, it goes hard as you put pressure on the wheel then suddenly it feels like a pop and the steering wheel jumps to the right? doesnt do it going left.

Its just passed the MOT so i cant understand whats gone wrong