When I said it jerked when trying to accellerate I should add that this happens when it's already dying and I put my foot down.
sounds like something other than iscv to me. fit your new one and see if it helps, otherwise i would start to look for vacuum leaks (air is maybe getting into the engine from somewhere and the ecu doesn't know about it so it runs lean and runs like shit.
let us know how you get on. have to go now.