Read the 8v digi tuning guide. Check all things like cam to crank timing, and ignition timing, which must be at 6degs if I recall, and requires no pre-advancing (ecu controlled). other than suggesting to go through everything, from fuel supply, temp sensor to dizzy leads, plugs, injectors, vac hoses, rotor arm + cap, have a poke about and see if anything seems dodgey/suspicious, or doesn't look/sound right. If it was working fine and nothing has failed, it could be a wire under your nose. You could remove knock sensor, clean block face then re-torque to 20nm if I recall correctly?