1988 Nissan Pulsar engine misses under load

1988 Nissan Pulsar 1.8 mileage: 500. Put a new engine in an '88 Nissan Pulsar, a 1.8 twin cam. When it idles, it runs beautiful but drive it out on the road up a small grade and it misses and cuts off. Took it to electrical tech. He made all tests, fuel pressure at 43 psi, vacuum, alt, fuel getting to fuel injectors. Nothing. They were stumped. I even put the problem online to other mechanics and got no answers. We changed computers, got used coils and switched them when it tested it. The only thing it said was it might be an open circuit in the ignition side. The new engine still won't go far.