My '79 zx is blowing black smoke, I have replaced the spark plugs, air filter, added injector fuel cleaner, all the injectors were replaced not long ago and they are fine. I have inspected all vacuum line for leaks etc. I took it to a Nissan dealer service shop. The mechanic there tested the fuel system, He found it to have too much pressure. He said that the FUEL PRESSURE REGULATOR was bad. I changed the FPR. Now you don't smell heavy fumes like before, the smoking decreased but there it still some black smoking during hard accelarations. (not quiet as bad). This smoke is black (NOT OIL Blue). The car does not burn oil. The car idles smooth and the acceleration is great as ever. This is the second 280zx that I've owned. I am familiar with Z's performance. Has anyone had this problem before? What else in the fuel EFI may be in need of replacement at 284,000 miles?