Thanks for the breakdown. That is super helpful to me because I am a very visual person and since I can't see what is going on inside the carbs I can't understand it exactly. I'm assuming that vacuum pulls the fuel through this system when operating correctly?

You know, I actually have done the above a few times and when I do it sprays carb cleaner through the idle circuit very cleanly and with good pressure so I'll have to step it up and stick something through the hole. Any ideas what to use? I asse I need something strong but thin.

when the engine is running does the engine respond at all when you adjust the idle air mixture screw on the bad venturi? don't stick ANYTHING into the passageways/ports, i.e. a paperclip or wire. when clearing out a jet blow the air opposite to the flow of fuel.

This is somewhat related since it sounds like the OP has had the top of his carbs on & off numerous times.

Anyone know where to get the weber IDF carb top gasket by itself?

I would like to have a couple spares but dont want to pay $30 each for the complete rebuild kits.

Yes, the mixture screw does respond on that cylinder. I wondered that too earlier in this whole thing lol.

I'll keep trying to blow air and cleaned through that vent hole I suppose :/

I completely agree it's bad practice. Unfortunately, it's next to impossible to blow air back on the idle air jet. Can't see how you can get an air chuck inside the idle jet hole to blow back up air jet. It's easier to blow air down from top and catch debris inside idle jet hole. If your not ham fisted you can mechanically remove crud without marring the air jet or plugging the short passage.

I'll see what I can do. I'm still not sold on this being the issue. I have blown through it a good number of times and it will blow carb cleaner through to the float bowl with pretty good force.

There's 3 holes that need to be clear. I made a quick drawing of the idle circuit for you. It's the top air jet you need to make sure isn't blocked.

If it's not that, I'm out of ideas.

Update:
Last night I put in a new seat and needle just in case. I also cleaned the idle air bleed and it is so clean you could eat in there now.

No change.

However, I did confirm my theory about the throttle plate. Last night after completing the above the carb started to gurgle again. As it was doing so, I grabbed the non-linkage side of the throttle arm (thing that the throttle plates sit on, no idea what the correct term is) and with a tiny amount of pushing I closed it just a little bit further. Gurgling stopped. Then I let go and the gurgling began again. I immediately pushed it again to see if the gurgling would stop and sure enough it did.
So the throttle plate isn't correctly positioned or closing all the way? Not sure.

I also have one more thing to add. Last I checked, the mixture screw responded to adjustments. I'm about 90% sure it was responding last week. Last night I tried playing with it and it is in fact NOT responding to adjustments. Normally I would assume this is a vacuum leak so I sprayed carb cleaner all over the place but was unable to get the engine to stumble.

You mentioned in your original post that you "adjusted" the butterflies on one of the carbs. I think at this point you need to check to see that they're closing all the way. Most likely the plate isn't aligned correctly in the bore. At worst case you have a bent/twisted throttle shaft. Take the carb off again, remove the top and the chokes, then place a flashlight in the bores in a dark room. You'll be able to assess how the plates are aligned and note any major passage of light past the plate.

If the throttle plate does not close all the way and in harmony with the one next to it, you will not get much, if any adjustment from the mixture screw as too much air is flowing past the throttle plate for the idle circuit to function.

I will readjust the throttle plate when I get home and I'll take a look at how it sits in relation to the lowest progression hole. What I'm now wondering is: if the lowest progression hole is open and exposed below the throttle plate, would fuel leak out (with engine off) because the throttle plate isn't covering it?

No. Look at the picture of the idle circuit I provided above. Fuel and air are drawn into the circuit by vacuum. With the engine off you have no vacuum. If the air jet is clear it will break the siphon and the fuel flow stops.

But like George said, you have another issue if your butterflies don't close all the way.

yep. the 4 progression holes are effectively blocked/out of the vacuum (should be) when the plates are completely closed. the bevel of the plates must be in the correct orientation or they are held open slightly.

Either way I'll look at the throttle plate and readjust if needed.

Can anyone comment on my earlier discovery about the throttle plate stopping the gurgling noises when forced closed a little further? Why would that cause it to stop?
(I'm assuming the gurgling noises and leaking are one in the same and when one stops the other will)

I am not as familiar with the 44 options.
Do you have the adjustable accelerator pump linkage?
If so, it would be easy to disconnect it to take it out of the equation.
And if you DO have the adjustable version, is it adjusted way too "tight"/far in?

Other than actually opening the butterflies, that is the only thing hooked to the shaft that affects the carb operation.

ANd if you took the any of the butterflies out, it is possible you bent the shaft.
And when you reinstall the butterflies, it takes quite some time to get it realigned.
I had to let mine "slap" shut a number of times to get them to seat properly before tightening the screws.

Again, with the engine off, no fuel should leak out of the progression holes no matter where the butterfly is. There's no vacuum to draw fuel and air through the idle circuit. That's if the idle air jet isn't blocked creating a siphon and your casting isn't cracked/porous.

Did you verify that the idle air jet was clear?

If your positive that your problem is a leaking idle circuit, I can't explain why the gurgling stops when closed. Unless, the "gurgling" your hearing is fuel running down the intake manifold and sizzling in the hot head.

Just send them to George. He can go through them, check for problems and even rebuild them for you.

Well I didn't get a chance to work on it yesterday but I have spent hours mulling this over while in the office at the day job.
It absolutely will not gurgle with the top of the float bowl off (gasket and metal float bowl cover that float and needle and seat attach to).
I have placed the gasket over the bowl and there is no blockage of air bleeds or anything like that. The gasket would have to shift a few mm in order for that to happen and that is certainly possible but I have looked into that and determined it isn't happening. Also since I have tried two different gaskets...

So the next piece above the idle air bleed would be the metal float cover that screws down with the 5 flathead screws. If there was a casting flaw or something on this piece that could cause an obstruction I wouldn't have caught it yet so it is probably worth a glance.

I have another trick up my sleeve that I will try tonight and report back.