Well.. It's kinda solved but now there's a new symptom. Now the 5-20% throttle range is smooth, but from 0-3%, ie initial tip-in there is hesitation/sputtering/misfire. And it does it immediately after starting even when cold. Car starts instantly and idles fine. Giving it verrry slight throttle will cause it to sputter/miss. More throttle and it revs fine. Interesting the drastic change in behavior with the new 02 sensor but not sure how to interpret. I'm thinking the 02 sensor isn't even active when the car is freshly started so I don't understand why the new sensor would cause this behavior. I'm going to triple check the TPS voltage, roller idle spacing, sparkplugs, etc.