Drew is the only one that I know of who as "played with" the Holley emulsion tubes.
I can tell you that with drastic changes of the emulsion tubes in a Weber 48ida you do get significant changes BUT there are three commonly used in 289's that are similar, F5, F7 and F11 that have only subtle changes at certain rpms.
In Webers, the location of the holes in the tubes effects the leaning or enrichening of the fuel mixture at one particular rpm.
Does that vary according to the engines vacuum draw related to engine size? Yes. The draw of a 427 is different then a 289.
Drew pointed out to me that the idle emulsion tube in a Holley metering block is used to keep the main circuit from coming in too early. So from his empirical method of learning Holleys, he has a different definition of an emulsion tube rather then a textbook one. Who am I to argue? I ask him for help and not the other way around?
That design happens to be Holley's application to their specific issue solution but not the traditional use of an emulsion tube.
What he told me to do is probably what you should do also. You need to remove the brass caps on the idle tubes. Those you drill out with a #1 drill bit.
New caps are available and reinstall easily. Now in theory you thread in a 8-32 screw into the top of the tube and pull it out. In theory.
Mine wouldn't come out and you need to go to the next step and use heat on the metering block. How much heat? 'don't know but keep in mind Holley metering blocks do warp just from engine heat and if they do, will leak past the gasket at the pump transfer hole.
Again, on Drew's Facebook page, he shows you what the removed emulsion tubes look like and take it from me, those are what emulsion tubes do look like.
You can see the holes in them, just like the Weber tubes at various heights.
Now don't ask me if they have different part numbers like the Webers do BUT one of the things that Holley did to that carb to make it acceptable to use on a 289 was "re-calibrate" it, which absolutely would include the emulsion tubes so count on the 3259 being just a little bit uniquely calibrated for a 289.
Drews point was that those tube transfer holes OFTEN are clogged and create crazy rich idle characteristics very similar to what you are going through with the carb right now.
Sometimes that shows in the response of the engine to the idle set screws.
I just went through this and still am. I have a little bit of a unique situation in running 2x4's on a C60A T/A intake on a 347. I'm set on 1-1/8 turns out and that's where that sucker wants to run.
What I think is happening with mine, I think, is that at 1-1/8 turns, it is idling partially on the mains. A purist will say, no it shouldn't, that's wrong but this intake has just a little different idling characteristics then a COBRA high rise does. It was never put on a production car and what I am experiencing MIGHT just be the reason? I don't think you could sanely use it with an automatic transmission at all.
It's difficult for the Doctor to tell if you are absolutely nuts or just a genius because he has no one else to compare you too? I suppose it is at least entertaining?
Now the point of taking out those tubes is to clean out the transfer holes and the idle passage at the top of the tube if it is located there. That orafice can be located in one of three spots in the carb. The one at the top of the tube is an .028 (look at your numbered drill set to see how small that is) and can clog if a cow in China farts 10,000 miles away from you?
My suggestion is to get Facebook just to see his page. He is a very helpful guy and readily shares what he knows but I think being offshore for 4 weeks at a time on a tug the crew and diesel fumes get to him and he starts throwing around wrenches if you piss him off? That would make me temperamental too for sure? Especially with a crew of 9 and cookie making fried Spam three times a day and only having condensed milk for your coffee the whole time? Yikes, I'm getting anxiety already?