As you sit on the bike. Cylinders are numbers 1-4 from left to right. Your plug photo shows 2&3 darker than the others. And, the shiny one appears wet either oil or gas. You should determine which.
2&3 share a common coil but they are also trigger by the same points set. Make sure the point set is adjusted correctly.
It is also possible, since you have vacuum synced the carbs, that the carbs on those cylinders aren't opening enough for those cylinder to pull their load evenly and this could effect plug deposits.
Could also be that the floats are sticking or the float height is wrong for the inner two cylinders.
You probably should start with a complete tune up doing everything in that check list before trying to fine tune carbs to an ill-tunned engine.
Because of the wet spark plug, I believe a compression test is also wise, as you will never get the engine to run well if it has a bad cylinder. Build a knowledge base beginning with a known state of engine cylinder health. Adjust valves, do a compression test. If those results are good, use new spark plugs, set the point's gap and timing, verify reliable spark at each plug.
THEN focus on carburetion.
These carbs have no accelerator pump. They rely on a slightly over rich idle setting, to overcome the rapid loss of vacuum and the resultant loss of fuel draw when the throttle slides are suddenly opened. The loss of air filter restriction reduces the vacuum and leans the idle mixture. Making the engine hesitate on throttle twist. (You will never be able snap the throttle open a get reliable acceleration. But, it should respond with up to one half throttle opening with predicable acceleration.)
In short, even if the midrange and mains supply fuel adjustments in the carbs are rich, throttle reponse is relying on a different part of the carb metering circuits for throttle response at low throttle/engine power settings.
More directly, you will need to modify your carbs or get an air filter back on that bike!
The pictures of the air filter and air plenum look to be correct for your bike. They assembled together and then placed in the bike frame (but, not bolted to it) prior to carb insertion on the front manifold couplers. (Hold it as far rearward as is possible.) The rear couplers are compliant enough to deflect (remove the band clamps completely) and allow the carbs to pass by them as they march across the front couplers toward final alignment. You will need to be careful not to tear those rear couplers already mounted the four air plenum holes. Once the carbs are fully inserted into the forward rubber couplers, then get the rear couplers onto the carbs, install the band clamps and mount the air filter housing to the frame with the right angle L brackets.
But, before you put the carbs back on...
Be certain you have the correct and unaltered jet sizes in the carbs, write down the slide needle numbers, and be sure the emulsion tubes behind the main jets are clean and clear.
Check, set the float height, as well. Mechanically align the slides so that they are all able to close completely with the idle knob backed out, then use the idle knob to open all the slides to enable start up.
Make certain the orings on the main jets are supple and sealing against the carb body when they rest on the emulsion tube base.
Turn the air bleed screws out 1 and 1/8 turn out from lightly seated.
Then put the carbs on.
I think you have some work to do...
