Could be a bad harness on the EZ, try disconnecting and check all the pins, try the truck without, to make sure it's the EZ. If re-connecting results in the same condition then a component of the EZ is faulty. Hope you didn't spend too much for it.
Does it do it on all the settings or just one of them? The reason I ask, I have an EZ that acts up sometimes on setting 3, but the other settings are ok. By acting up I mean my rail pressure would sometimes get very erratic, and sometimes drop to zero. The truck never faltered, but watching the rp gauge would make you nervous. The EZ circuitry boards are not of the highest quality, and do break down.