have you checked the wiring loom to the injectors as this can cause this problem check the plug at the front of the rocker box drivers side up under disconnect and look at connections if oily also check the loom to the ecu as it is a known fault with this engine that oil will back along the wiring to the ecu causing misfiring and poor starting clean the plugs, i use brake cleaner,and replace the loom inside the engine .you may have to have the ecu cleaned \checked.
bleeding the system ,switch the ignition on fully depress the throttle pedal five times, the eml will light up and the system will purge leave until the light goes out.hope this helps.