Yes you should set the gap with no venturi in the carb.
The bottom of the venturi doesn't seal the carbs barrel so it's not correct to set the gap according to the venturi.

Grizz1 even if the idle gap is wrong this doesn't explain the lean bog i experience.
Of course your method is better in judging if the LSN is at least too Lean or too Rich since the load up metod depends on idle gap as well by altering the overall settings.

When do you pinch the fuel line:
-right after a WOT run
-or after letting idle for some time(for how long?)