The DIS is grounded through its lower mounting bolts to the intake. So, the intake must be grounded for the DIS to function. There should be a ground strap running from the rear passenger side intake support bracket to the firewall. Make sure it's there with good connections. There are also a couple brackets between the intake crossover tube and plenum that must be bolted tight. Basically, you need a path between the lower mounting bolts and the negative battery terminal. If you have an ohm meter, it should be easy to check. There should be no resistance between the lower mounting bolts and the negative battery post.