code 43, how to diagnose this code.

In addition to the code 9 from the flashing D4 shift indicator, after driving the car for a couple miles on the highway, the check engine light comes on, giving me a code 43, fuel supply system. I have replaced the fuel filter, and dispite the light being on, I have taken the car to 95 mph and no signs of fuel starvation. Please help me in trouble shooting this code. BTW, i have also replaced the vehicle speed sensor and the distributor, and with the same end result.

code 43 may not just be a fuel supply issue, but also a 02 sensor issue.

maybe ur fuel pump is going bad intermittently...or faulty injector....hard to say, u really have to get a voltage tester and also test the resistence.