I have installed the Perry Oscillating gasoline pump and a Cline regulator on my Saito 150 but have not mounted it yet for running with the pump and regulator.

This should make the needle valves stay the same no matter the attitude or the fuel level.

But this does not address the rich spot in the mid range. One way to approach this is not run the engine in the rich area?

According to TKG this is caused by the position and shape of the cam groove in the carb barrel.

I found the Saito 150 to run very nice on gasoline with the stock carb except for the rich spot around 4000 rpm