After installing AEM ignition coils on my RX-8 the engine won't idle. Do I need a remap?

Usually no remap is needed, unless your ECU was already remapped in the past with specific dwell settings. The symptom you describe is unlikely to be caused by the coils themselves. Refit the stock coils: if the problem remains, look for another cause (vacuum leak, sensors, spark plugs, wires). Tell us the result and we will help you further.