damn looks like I need a new O2 also. I have this problem, just not as extreme. RPM would jump all the way down and almost shuts off after I step on it during warm up. Sometimes when I'm boosting real heard, my car would start to run rich, bog and eventually misfire. So hopefully it's just the O2. My af guage won't read right at WOT unless I'm on the highway and going on the gas slowly. As soon as I reach 10psi and over, the a/f guage would jump donw to .1xx.