There is no cut and dry answer but to get an accurate answer the proper tests need to be done. You should do a compression check on all cylinders for comparative purposes. They should all be within 10% of each other. If the compression is low the first place to start is the valve clearance, the easy stuff first. As far as the good spark good fuel, how was that determined?does it pick the cylinder up as the rpm increases? If the compression is good you need to put a vacuum gauge "carb sticks" on the throttle bodys to see if they are in sync. The best way to get definative answers on the running problem is to get some with a exhaust gas analasys machine and put a port in each header tube. Your Co levels will tell you what is causing the miss fire or not running at all.