84 FJ600 - Clogged Idle Circuit for Cylinders 1 and 2?

Observations: Recently got a colortune and noticed that I am not getting consistent combustion (read this as mainly no combustion with a sporadic flame here and there) for cylinders 1 and 2 during idle. I can still get the engine to run and have decent responsiveness when opening the throttle. When I do open the throttle then I get consistent/continuous combustion in the cylinder (yellow/organge flame so its rich). I also experience a rev/rpm hang until I blip the throttle and the rpms will drop back down to idle.

Thoughts on problem/solution: So my go-to thought on what's wrong is that the idle circuit for cylinders 1 and 2 are partially or almost clogged and therefore not receiving enough fuel to combust consistently. Since I can get the engine running, I've set the idle speed to ~1200 rpm based solely on cylinders 3 and 4. Once I get the rpms up, the main circuits on 1 and 2 kick in and give the engine extra power. Since the idle was set most likely high due to being based on only 2 cylinders, it wants to stay high now that it has all 4 cylinders combusting. Some how blipping the throttle interrupts the rpms enough for the main circuits of 1 and 2 to cut and then rely on the idle circuit and going back to almost no combustion, ie engine running on only cylinders 3 and 4.

Known: I know there is good spark in cylinders 1 and 2 because I can see it with the colortune. Diaphragm slide bores in the carbs have been polished and they "drop like a bag of rocks". Carbs have been synced with gauges. Valve clearances fix to within spec.

Would love to hear yalls thoughts on if I am on the right track to fixing this problem or not. I'm going to do a deep clean of the carbs no matter what but thoughts on other possible causes would be much appreciated. Thanks.

 

Get a spray can of carb cleaner and direct small spritzes at all eight throttle shaft ends, around the intake boots, everywhere on the engine side of throttle plates to check for vacuum leaks.