Is it that "CO adjustment" screw in the fuel distributor, and if so, what size and kind of tool (t-handle allen hex) fits?

If it's by fuel pressure only, does anyone use an adjustable pressure regulator in paralle with the thermo/electirc control pressure regulator?

I can break the regulator input line, attach them to a tee and bleed pressure off that, then return it to the return line at another tee.
Nylon 'air brake hose' works great for fuel lines, and can be hot-water fitted to the barbed connections.

I want to tune for gas mileage, and maybe compensate for fuel grades. It never pings. There's some scary gas out there.