TOPIC:

First- there's usually needle valves on the vacuum tubes ( up near the base of the gauges) to dampen the pulses to the point that the needles are steady.

Second- the first and third gauge readings are out of sync to the second and fourth by what "looks like" 1/2 inch and it's close but if you have all the tooling on you should be able to get them just a little closer but it's hard to tell with all the needle bounce.

At least you are allowing us to see how your making out. Many of the newbies that show up here ask questions and never let us know if the info provided actually helped so THANK YOU for being kind enough to follow up.

Let us know how you make out please.
KB

Did you calibrate the gauges before syncing?

Thanks for the encouragement kawboy, hopefully soon I’ll be giving the all running good post!

Calibrate in the sense that I plugged them into the same cylinder and got pretty close readings from each gauge.

Colourtuned each cyl, to a nice blue, got each one to about this: youtube.com/shorts/ET7RMmnMd_o

then when on the carb sync, best I got was this: 

and another one not quite as close: 

the exhaust is popping occasionally now, can hear it on the 2 vids, not sure if that’s good or bad, but equally I had the air box off during this, will put back on tomorrow and check again. No chance of getting it to idle any slower though.

My $0.02.

You're trying to achieve too high of a vacuum.  .....10"Hg is (obviously) achievable but you now have the throttles closed so much that despite the 10" the "pulsing" is playing havoc with the ability of the pilot needles to distribute an even and consistent delivery of idle fuel.......in spite of what your Color Tune is indicating.  Back off the sync -adjusters and go for 8". The idle RPM will need an adjustment but the end result will be a much smoother idle.
 From my own experience I've never been happy with the results that I was experiencing with 10"        ( of vacuum)   

My #2 set of carbs (57+  MPG at 95 to 100 KPH)  are sync'd to 8". 

I’m working on this now, but struggling, I back off the balancers, rpm goes up, back off idle, vacuum goes back on, got the balancers pretty much all the way out and still around 9 inHg, at best with some going above 10

Check your Gaps on these two critical adjustments.  The .54mm/.55mm .is  in my opinion  NOT correct ... 
I have found that 2.mm or something in this range is more suitable. 

www.kz1300.com/index.php/carburators-fue...idle-adjustment#8187