Mine for sure don't have pvrc,(Changeable chanel restriction) and i don't think it has a brass IIRC And i barely know what these letter stand for. Let alone how changing them would make it better or worse.
Fixed drillings IIRC, probably best left alone unless one really knows their ****.
So yes LTFA, AKA not touching them.
My demon carb is too old to have the Idle Eze on it, but it has 4 holes drilled in the butterflies already. (one per butterfly)
Been reading my holley book" Holley Carburetors & manifolds" by mike urich and bill fisher.
Just trying to refresh my mind on the butterflies hole drilling and the air/ high speed air bleeds.
I hope the holes drilled in the throttle shaft butterflies his big enough for the smaller main body. They were border line with the stock 850 Demon.
The mixture screws were adjustable, but the curb idle had to be raised above the square transfer slot setting i set before installing the carb. had to open up the primary and secondary idle screw to get it to idle.
Just for reference. I had a 5.5 power valve in the front and when i jetted the main jets up, i when to a 4.5 PV. It idles in neutral around 7 to 8 inch of mercury.