Did they give a rationale for the throttle extender? It seems like that would make it less "touchy" by giving you more pedal travel, but is that the problem you are having?
Where is your O2 sensor? And what intake are you running?
I am wondering if you are getting some weird effect from the location of your two injectors relative to the routing in your intake?
The measured AFR is an average across whichever cylinders are joined before the O2 sensor. You could be getting some unexpected results from that, maybe?
