ford ka pulling back on accelleration..hesitating?

hi.can anyone help got a t reg ford ka 1.3 petrol multipoint injection...car starts pulling back and jerking when accelerating.replaced new plugs,leads,coil pack,cleaned the idle control valve put redex in tank all to no avail..it does feel electrical to me..now when i renewed plugs leads and coil pack it did seem to run a bit better but still not right..has anyone any ideas..no engine management light on by the way...would appriciate any answers many thanks....karl.

karl
April 2008