Holley fuel idle trim setting

If it runs correct there run it. There are several factors that determine how far out you adjust the idle mixture screws but generally 1/2 turn to 1 turn is about right. 2-1/2 turns would be really rich in most cases.

BTW: if it's an automatic I suggest adjusting the idle mixture screw in gear. Adjusting for highest idle vacuum in neutral will generally result in a slightly lean mixture in drive