Code 43, can't figure it out!!!
 

So i have been dealing with this problem for about 6 months. I am getting a code 43 in my 91 GS teg b18a1 OBD0, In my manual it says that it is a an oxygen sensor problem or a vacume leak. I have noticed a loss of power. When i am driving around town the CEL does not come on but if i am above 3000 RPMs for over a minute it will come on. So far I have replace the Oxygen Sensor, Vacume Tubing, Fuel Filter, checked all my grounds. Could my ECU be bad? How could I check? Please help.

check fuel pressure.

could also be dirty injectors and intake caron build up in the intake manifold.

Is that the only code you're getting? I got that on mine, but was also getting one for the map sensor. Replaced it and all was fine

i installed an adjustable fuel pressure regulator and have it set to 52psi, stock is 41-48, and i have also ran injector cleaner. I also removed the fuel rail and injectors and cleaned and inspected them, everything looks ok, this is why I am stumped.

did you ever figure anything out with this? I am having the same problem.