I have the new AI 1.9 with ten shelves. Does using nitrogen help prevent muffining, allowing to utilize more shelve space earlier in the purge? What effects does adding nitrogen exactly have on the overall purging process? I’ve found that I have to space my shelves out early in the purging process and than later am able to stack them closer together. I’ve heard the nitrogen helps in this process. Any advice would be great! Thanks. 
controlling vacuum depth to avoid muffining helps.
you can certainly achieve that by leaking nitrogen in, and sucking as hard as your pump can manage. then gradually turning down the nitrogen to increase vac levels.
It would certainly be better than leaking AIR into the oven to lower vac levels using the vent valve.
I don’t see that it would be significantly better than putting the leak (using a needle valve or an actual controller) outside the oven, and closer to/at the pump. where you can use air.
backfilling with N2 when you open to flip or pinch, or whatever is not necessary, but probably wouldn’t hurt.
plumbing N2 to your vent valve is the simplest way to achieve N2 backfill.
control of the muffin has to do with temp in the oven vs relative melting point of your oil (and a bunch of complex cohesion forces), as the temp is increased, more of the oil is melted (ie the low molecular weight terpenoids phase change from solid to liquid), thereby reducing cohesion forces that allow the oil to stay solid, allowing for gas vapors to escape, leading to less stable bubbling, thus less muffin.
Nitrogen blankets are useful in other ways, IE removal of Oxygen from your oven, reducing the oxidation of your oils leading to terpene loss.
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On startup, muffining has more to do with vacuum depth.
For now I ramp manually. By sealing the oven and turning off the pump at various depths, for semi-standard time periods.
I’m on the fence as far as achieving that with N2 backfill into the oven. IF it was automagic, I might be more interested. Taking the human factor out seems like a win. mostly.
Might get around to programming a controller to controll vac depth at/near the pump. Or looking to see if I can get something off the shelf.
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Thanks for your input guys.
What’s the advantage of the cascade kit over just a regulator or 2 to hold it at ~10 psi?
Is there any difference in muffining between letting in air vs. inert gas or is it more for color and oxidation?