Very rough running

HELP!!!!!! My car sounds like it only has four cylinders working
there is a regular beating sound coming from the back box. The plugs are only 3 weeks old (NGK PFR6G-11) the info on the net said do not gap so i did not gap! I have taken off the coil packs and found that one of them has both conductors fully exposed at the base where the wires join the coil pack, could there be any arching across these two points,would that explain the rough idle. Do svx`s lose pistons? The coil packs have never been changed (car registered 1992) I am open to any advice.
If I need new coils, any idea where to get them from. i repeat HELP!!!!!!