3000gt running rich and back firing

Hi I just got another vr4 that is running rich and backfires through the exhaust. I replaced the spark plugs, wires and o2 sensors. I tested for air leaks and I didn't find anything. If someone could help me out it'd be great. Thanks

What year is it? If its 91-93 you need to check the capacitors in the ECU.

Yeah its a 91 I already checked and replaced the capacitors.. forgot to mention that. But it is still the same.