I have a 1995 Civic that is getting a MIL Code 43 from time to time when I drive it. I have found that it stand for Fuel System Malfunction, but I can't find any information on what to check to get it fixed. Does anybody know of anything I can check the get it fixed?

It's either a problem in the Heated Oxygen Sensor circuit or a problem in the Fuel Supply System.

Does the fuel supply system mean the fuel pump?

What is your car experiencing? That will tell you whether to focus on the oxygen sensor, PGM-FI main relay, fuel pump, fuel injectors, fuel filter, or fuel pressure regulator.

The car doesn't seem to change at all when the check engine light comes on. It might idle a little better but that is about the only difference I have noticed. A little background: Its actually a 2000 civic si with an obd1 ecu so that I could use a piggyback computer (hondata s200) to tune the car. It has been fully built and has 750cc injectors rather than the stock 245cc and I have upgraded the fuel pump to a 255 lph. I have a custom exhaust that I welded an O2 sesor in the side rather than the top so the wires for the O2 are sretched tight but all are still in tact. I assumed if the O2 was the problem I would be getting a code for the O2 sensor rather than the fuel supply system. I had never seen a code 43 and its no longer listed in the OBD2, so it confused me.