03 jetta primary coil malfu.

I bought this 03 Jetta with a 2.0L and this code keeps on popping up. P0351 and i replace the wires, plugs and the coil pak thinking it would solve it but it returned again 4 months later. i return the coil pak and got another and this time it lasted about 1yr. What would cause this to keep going out or is their a major coil pak problems?