I dropped an 83 280zx motor in my 78 280z and i have had nothing but problems.The zx motor ran perfect when i pulled it out and only has about 65k on it. i wired in the zx ignition swapped the old z ecu with the zx ecu.and went to start it .it started right up but ran awfull.the plugs were fouling the engine was misfiring when i took it out for atest drive. the fastest icould get the car going was 40mph. when i pulled it in the garage and shut it off i tried restarting it and it didnt start it didnt even sputer. then i let the car sit for about 2hours and it started up after it was cool,but still ran like **** .i have to give the car gas in order to keep it running. i let it run for about an hour and then all the missfirig and stumbling stopped and it ran smooth ,but when i revved it up it started running like **** again.and it did not start when i tried restarting it. im thinking it might be the mixture but that doesnt make any sense because the motor ran perfect when it was in the zx.I have raplaced the usual,wires,plugs,rotor ,cap,fuel filter, checked for vacum leaks,replaced all the gaskets throughout the motor. but i still cant figure out what the problem is. If anyone has any ideas to what the problem could be please contact me. Im dieing to get this sweet ride going.