I have spent the past week reading about these carbs and playing around with mine, so the following info is just me interpreting what I got out of it and tinkering with it to experience the effects I have been reading about.
The thing I have noticed with these carbs is that you have to adjust every range. Just because your plug is brown doesn't mean you aren't close to seizing it at mid throttle.
The main jet controls 4/4 throttle only. I would start it, then pull back on the throttle all the way and let it bog and die. Pull the plug to see if it's wet. If it is, then a smaller main is needed. If not, a bigger is needed. You can also use the choke to check this condition. If it bogs with the choke, downjet. If it runs better, upjet.
As far as the pulling, you can hear and feel those kits running lean, and IMHO, Polinis are verrrrrryy perschnickety. A ridiculous pull can be a symptom of a lean condition (and if it was me, I'd be a little weary of it). If controlled, it's no biggie, but if you are running lean at 1/4-3/4 throttle, it's going to end up as a big ol' FAIL. I've got the 21mm PHBG-R, and I'm running a 104 as well. Bogs and dies at 4/4, but that could be because my idle jet is tooooooo small. I would guess that's where you would want to focus your attention first.
As far as features on these carbs...a quick run down...The taper, diameter, and point diameter have VERY specific jobs (please see the links below). The top notches in the needle are used to delay, or lean the mixture during throttle movements. Notches at the bottom will advance, or richen the mixture. The needle will affect the throttle enrichment all the way to 3/4 throttle, then that's where the main jet kicks in. The Idle jet is responsible for circuit transitions and is IMHO, the MOST important element in tuning these carbs. It is also responsible for the first stages of throttle movements, as well as, well...idle.
Here are some links: