Thanks Brent.
I'm not sure what needle I have either. It was a long time ago. We were shipped an economy kit that was sans a couple of parts, so gave it back to the distributor and got a replacement which I didn't install for some months.
The only way it makes sense (to me) to get leaner/hotter at WOT is if the main jet is the WOT bottleneck. So that 5-minute screw out of the bottom idea would be what you did to the main jet? or the (above it) needle jet?
I've never pulled a Bing carb to bits on my own so I don't know much. To me it looked like I should be changing the main jet, which is at the bottom, and looks (from the drawings) about as simple a job as you describe .....