Problems with PVA print on Taz Pro

I am having problems printing PolyDissolve S1 (PVA) supports with a Taz Pro. (Actually a Pro S with dual extruder installed.

Last problem first because it concerns me most. I have quite a lot of burned PVA caked on Extruder #2. The printhead nozzle seems to be clear but the surrounding area is black.

Is this bad for the machine?
How can I clean it?

The next problem is that the PVA will not feed consistently. The Idler Adjustment Knob on the M175 print head is rather touchy feely (Hand tight and back off 1-2 turns), The Dual Extruder’s have indicators that should be set to the middle setting. Is this absolute or merely a starting point?

I was trying to print my entire supports with Extruder #2 (PVA) but switched to Extruder #1 (PLA) supports with only the “roof” printed from Extruder #2

In either case, I will either get “Extruder 2 Filament Error” or the PVA will not stick and forms curly clumps. Often these clumps are darkened like they are partially burned.

The only thing I have tried so far is trying to adjust the Idler adjustment knob and I have no idea what to try next.

Dual Extruder
#1 Hatchbox 3mm Glow PLA using Standard PLA (3D Fuel) profile (Diameter corrected)
#2 PolyDissolve S1

The only humidity control I am using is storing the filament in vacuum bags with dessicant. It has been sitting out for 3 days on 25-55% relative humidity.

As far as the idlers go, there are no absolute rules, it is just what works best for the material. You might do a temperature tower and other similar prints to find out the best profile for your set up. My only recommendation for cleaning the nozzle is to heat it up then turn off the printer and use something to scrub the residue off. Keep in mind that there is an electrical circuit that will be made if the printer is on and you use something that is conductive to wipe.