If you think it is a pressure problem, just measure it.
When the plug is removed, along with the hard plastic sealant below it, it can then be adjusted if needed.
When the plug is removed this introduces a the tiniest of air leaks as the top half of the reg is connected through the vac pipe to the inlet, but certainly not anything you even need to consider it's so insignificant.
There are two diaphragms inside seperating the top(vacuum) and bottom(fuel) half of the reg, if just one goes it will affect it.
tabetha