I am working with a 1987 Snow Commander w250, 318 throttle body. bosses truck. started running ruff and slowly got worse keep tell him we need to get it in and look at it, not till it died on him going up the road and he nursed it back to he shop. said throw a set of wires on it, so I did his diagnose not mine, right, so I have been living with it ever since. ok, replaced the coil and pick-up and it ran great again except for the warm up after that it was good three days later it dies again and now the cat. is rattling so clean it out. again runs great after the warm up at cold idle and fifteen too twenty min. in it is a ruff beast. Ideas?