I would check all the fluid levels to start with , the fuel pressure,the belts , I'd double check the plugs and wires.Then one by one I'd remove the plug wire going to the coil and clean the connection with a wire brush , sandpaper and a file be sure that you do this one at a time and brush off any remaining sand etc.If possible I'd make up a diagram for these plug wires and unbolt the coil , unplug it and check it's housing for any cracks or bulges or dis-colouring all are signs of a bad coil.
Hope that helps and best of luck.By the way check the air filter , also clean the charging system on that vehicle and I'd treat the fuel with something like STP or Lucas fuel treatment, then after using up a few tanks of fuel change the gas filter.
