Holley Carb/squirters+jets ?

Could someone explain to me when it's appropriate to mess with the squirter size, and when it's appropriate to mess with the jets? I'm somewhat confused as to their specific functions. Currently, I have a 750 Holley (flows 930) which has a 42 primary squirter and a 37 secondary (mechanical). Jets are 76/78. Manifold vacuum is 9mmHg. PV is a 4.5 Initial timing is 18 and total is 38, all in by 2800rpm. Car has a mild stumble off the line. Any info appreciated.