I have a question about A/F readings and a cam

It's not the cam.
IMO,Way too much initial for the size of cam.
See below.

Unless you are trying to idle it way too slow, or are running a singleplain.
Then the whole shebang can conspire to wreck the idle AFR

Well, I guess it could be the cam.
If the intake opens way too early, and,you are running a SP intake, and the idle is way to slow.
But none of that applies to you. You have a DP and idle at 800, and unless you installed the laziest cam in the world, the intake closing angle will be fine.
The tip off is when you said;" as soon as"..
But at 800 with the throttle closed, those pistons are sucking so hard they're about ready to suck the bowls dry right through the idle-ports.BaBaam!

Wait, is there an echo in here? Hello... ello.....elo..........looo...................lol!

Pull her back to 12* to 14*,close up the secondaries tight, and, you guessed it...................Set the T-port sync.
Rev her up to around 2400. Reset the mixture screws for highest rpm. Drop her back to idle. Use the T-port to add or subtract idle fuel to get a smooth idle. Adjust the secondary opening to drop the idle down to something like 550 to 650 in gear.Reset the transfer opening if you have to for smoothness; leave the mixture screws alone.
TB you know me, would I steer you wrong?
Ok truth; Thats how I set mine with a 223/230/110 cam; Did I mention it went 32mpgUS in O/D? heehee.
Oh yeah, All in by 2500..., Ima guessing you have a hi-stall,Or you might not get away with that on 87.
For very long.....