It's only 140 bucks for the ls2(Correction:LC2). I understand how it feels like cost escalates, but the Wbo2 is one of the best things to get besides efilive. It comes with a weld on bung, so I mounted move on the driver side about two inches behind my regular 02s.
That being said, there are definitely people who have tuned part throttle on the STFTs, I think if you search "narrow band tuning" that should hit it. So got to do wot tuning though which narrows can't help with.
Timing jumping at idle is most likely due to active idle tables. Ecm is constantly trying to maintain the set rpm, but if your rpm is set too high or the range of spark is allowed to cycle too far then it will jump. When I get to my laptop I'll take a look at the maps that I altered for the idle timing, when I get to my laptop I'll take a look at the maps that I altered for the timing, every time I've responded I've been on my phone.