Just as title, the vac control - the disc shaped thing W/ 3 vac lines into it that connects to the EVAP canister is buzzing at idle. When I give it any throttle at all, it stops buzzing. What could be causing this? Is it controlled by the ECM? Are there parameters I can adjust in the chip?
I'm running ARAP at present, and this doesn't seem to present any driveability issues.
Thanks for any help

 

You are describing either the tank pressure control valve or EVAP purge valve. If the throttle stop position is set a bit too high, this valve(s) will receive partial vacuum from the ported vacuum source on the throttle body when it should be in the idle position. Moreover, the EGR solenoid will receive parttial vacuum, and if the EGR solenoid is duty cycling, the EGR may try to open at the idle position.

This is yet ANOTHER reason not to try to increase the throttle minimum air position too much above the specificied setting.

 

Thanks for you reply Vader, it turned out that there must've been something wrong with the valve. I replaced it, and all is well. Thanks.