Whats going on with my A/F??

I've been dealing with carbon fouling plugs so I decided to finally install a Wideband in the car to see what is happening. Specs are as follows

LA360, XE268H Cam, stock pistons, Magnum heads, air gap, tti's, qft slayer 750 carb. Timing is 20 initial and 35 total.

I swapped the idle air bleeds in the front to 74's and the rear to 43's. 4 sizes larger as a recommendation from QFT.

Initially, before the gauge I tuned the car to the highest vacuum reading I could get. Which was only 13.5. Upon first start up, after the gauge was installed it was reading 10-11 on the gauge. So I readjusted the mixture screws and got it reading from 13.2 to 14 at idle and in gear 13.8-14.8. This was not at my highest vacuum reading. It actually dropped my vacuum to around 12. If I tried to adjust it to a higher vacuum reading at idle, then when I would put it in gear it would be in the high 15's to 16's.

I took it out for a drive and the first thing I noticed is coming up to a stop light it sort of stumbled, when I went to take off. I looked at the A/F gauge and it was in the high 16's. I continued to drive and at highway speeds the A/F guage was from 12.6 to 13.9. At 60mph Im turning 3k. I tried to find out when it would switch from the idle circuit to the main and its around 2200-2400rpm. Which is around 45 mph. Faster than that its on the main circuit. Cruising the idle circuit is about 13.2 to 14.0.

So I continued my drive and noticed every time I came to a stop light or stop sign, especially after coming down from highway speeds the car would stumble and the A/F would spike up to high 16's and 17's

I got home and shut it off. I let it sit for a few minutes. When I started it up to pull it in the garage it was in the 12.6 to 13.9 range. I pulled it in the garage and it shot up to 15.4 and going blank because it was out of the range of the gauge. I reved it a few times and it would drop but continue to go back high, so I readjusted the mixture screws to get it back into range which was about a 1/3 of a turn out. So now I think I threw off the cold start settings.

I dont understand what is going on and why the large range on it. Especially after coming down from highway speeds to a low speed.