slo_hatch

ok...i searched but didnt find a whole lot. lol i got lazy. ok here's the problem...i have a 93 cx hatch with a d16z6 swap. i had to hardwire the 4 wire o2 cuz the cx came with a 1 wire o2 sensor. i had a shitload of problems with re-pinning the ecu. now the swap is done and has been for a longass time. but im still running RICH!!! im gettin like 20-25 mpg while driving conservatively. i swapped out the o2 sensor with a used one from a local honda junkyard. it helped for about 2 weeks maybe...now its back to its usual self. running rich and smelling like gas and throwing code (dont know exact code...havent checked it lately). im thinkin bout goin to buy a bosch direct replacement o2 sensor from advance to see if this fixes it...but what could it possibly be if its not the sensor? could it be the wiring itself?