"Since my lean bog is specifically on idle -> on throttle
situations, ..."

I went on a trip to Sweden last year with my Amazon, 1200 miles each way and a couple of hundred in between. The idle was not good for a stock engine, but it drove very well. Some time after I got home, I constructed a simple lambda-sond driven mixture monitor to make adjusting the carburettor a bit easier. What did I find out? I had been driving all these miles on a really lean mixture, without ever noticing anything but the erratic idle (and the car running a slightly hotter than it used to, but nothing to worry about).

Moral of the story: even if your mixture is lean overall, you won't necessarily notice it in driving.

The separate idle mixture screw only allows for very small adjustments. If the mixture would get more than a tiny bit richer by changing the spring, the idle screw will be useless.

Joris