your signals were probably erratic due to poor metering up front , not to mention a bad metereing job is made worse by extra non metered air.
KEEP UR MAFS MINTY!
as for the OP issue , i would say to see if you can get a tech2 hooked up , for cheap , and see your o2 crosscounts. if its rediculously high , i would say clean your maf , if it looks normal , you may have contaminated the o2 sensor.
can i get a pic of this spark plug setup? i think its what im looking for on mine..