RE: Pump pressure setting?
GN:
In response to your questions about the LS needle.
The HS needle sets the maximum fuel rate with the throttle full open, and naturally, as the throttle closes off allowing less air into the engine the amount of fuel has to be decreased at the same time. The restriction of the LS needle is what changes this, and the taper controls the rate of decrease. Changing the shape of the LS needle will upset a good running engine, but sometimes a poorly running engine can be improved by altering the shape.
If you make a study of these simple/sophisticated carbs you might want to experiment, but a blind change will more probably hurt than help.
Bill.