40:1 instead of 50:1 will slightly lean the fuel:air ratio. The carb meters not just gas, but gas with oil in it. If you put in more oil there's less gas per unit of air. 50:1 to 40:1 is not a big difference but if it's already lean it's going the wrong way. Not that I'd suggest 100:1 oil ratio to richen up the fuel- it needs enough oil.
Race gas will reduce the chance of detonation, which is one of the bad things that can be cause by running too lean a fuel ratio. But fuel atomization also cools the engine quite a bit in two strokes. Lean fuel will mean less of that, and race gas won't help it. Race gas is really expensive. And it won't fix poor running from being too lean.
There are tools available. I've seen them on Amazon and ebay. Or you can make a tool or an adaptor. For a blower that came set up way too lean I made an aluminium cap that fit over the splined adjuster and has a screwdriver slot on it.