So I've been doing some looking around and I've understood the first O2 (upstream) is for A/F and the second O2 (downstream) is essentially for checking if the coverter is working. I've been having a problem with really bad LTFT like down in the -20/-30 percentiles and my car was recently up at the mechanics and he said I was reading 14:1 AFR at WOT I emailed my tuner and he assured me I was not. He sent me a revision tune and I'm still having my problem. So my question comes, will doing the sparkplug non-fouler trick will AFR if I did it to the upstream sensor? In hopes of decreasing LTFT.