93' cavalier, very rough running. Missing badly at all speeds and loads, including at idle in park. changed plugs and no change in symptons. Is this an injected motor (4 cyl)?

Yes it is fuel injected. If it runs but has no power there is a good chance that an ignition coil went bad and there would be no spark to two cylinders. Cylinders 1 and 4 are partners on the same coil and 2 and 3 are partners. Usually these cars if an injector goes bad they have an external leak.
You can try to listen to them by holding a screw driver to each on while its running but I don't think
that will be your problem anyway.Another giveaway for the coil could be a gas smell like it is partially flooded. When you changed the plugs were any of them wet with fuel ? There is also a chance that if the engine works ok at highway speeds that the egr valve is stuck open. This causes
rough running at idle and bad hesitation until highway speed is achieved. Hope this helps or let me know and we'll figure it out.

Paul