I dont think you have to mess with the jet.
The assisted valve, well at least on a long rifle like mine, if you screw it in a little, then yes it will close faster and behave like you will not want.
Same go if you adjust it a little more out so it is open longer, even in the long version like mine, though in larger calibers that might be different, but i also see unwanted behaviour then and waste air.
So in my long pea shooter case, the valve need to be flush with the end, or be very minimal from that, though i dont think i would be able to tell the difference then.
But we are talking mm here, and only a couple of them at the MAX
A few 1/10 of a mm either way i dont think i would register, but a mm or a little more either way that i do feel.