Wire zapping manifold shield

Looks like you have bad wires causing that. As stated spark will follow the path of less resistance to ground. I run the Accel yellow wires on mine that you install the ends yourself. Fairly cheap and never gave me troubles.
I personally find these to be junk IMHO. Go with the similar kit Taylor makes. they have alot of boots and everything. what happened is probably you burnt a hole in your wire and are gonna need some 90* boots on those wires to keep the far away from your manifolds. No offense to your Chryslerfat, just saying, I like the Taylors better as they are a better made product.