i think you would find that that is an exception rather than a rule polo.
obviously things will fail for what ever reason, but all in all they are one of the best ignition systems around.
non cdi coil on plug will make a little difference,more so to drivability/chrispness than out right power in most cars(maybe a slight power increase)
harry I think you will find that you have an underling proplem (as you said yourself maybe the loom)..stock coils can easily handle your power and quite a bit more for that matter. save your money and buy a loom first man.