I've been working hard on trying to get good fits with glass parts on my herbalaire and these past few days I've be on to something. The way I think and feel about things is that some engineer worked on the HA to make it what it is so I cant go and throw everything out of the window but I've got a few place to start now.
1. The screen in the main Teflon and bottom of the HA crucible are shit quality and coarse so lazy people don't have to clean them often. This is an easy fix just buy a bunch of different STAINLESS STEEL screen that are fine or micro fine. The difference is huge.... No tiny particles to irritate my throat and vapor quality changed. This is something that will create restriction keep in mind.
2. HA uses shitty stock tube. Its thin in comparison to other vaporizers and it taste/smells like crap. The best tube to use from my experiments is the tube made from good silicone not surgical silicone(only 400f) you need the food silicone (500f). I found some on amazon and ebay where you get it is your choice. Here is the specs i use: White SiliconeTubing, 5/16"ID, 7/16"OD, 1/16" Wall
3. In side of main Teflon is very narrow and so is the straw. The straw has got to be the biggest pain in the poop hole since it gets sticky and nasty. The best thing i could find to do with it was pop the old screen out of the main Teflon and take of the straw. next drill through the whole thing until it seems like the Extreme Q mouth piece will fit but its to tight to enter. Make sure you don't drill enough for it to fit since you wont get a seal like this. Now the tricky part: get tongs or pliers and submerge the Teflon and glass in hot (almost boiling) water for a minute and then carefully push the glass into the top of the Teflon. It will be tight and may need to be re-submerged many times to make a fit. once this is done let it cool and cover one side and blow through the other. There should be zero pressure leak (mine Holds 90psi from the shop compressor)... probably more to but I don't want to test that). Once that's all done and said, clean real nice throw on some quality screens ( I use 2 micro-fine SS screens in the main Teflon). Then throw on the good silicone hose and your machine has some serious performance gains.
Here's what the piece should look like after mod: