Sb400, Cam specs, duration @ 50, 224 224. Adv duration 298 298. Lift.465 .465 Lobe separation 107 117. 15inhg at idle. Holley 670 truck avenger. Have leaned the idle mixture out as much as possible at idle with the Engine still running. Plugs come out black. Sea level, low 30s to low 40s outside temp. How many jet sizes should I go down?