What is the correct adjustment for adjust the FIT valve ?

Should I tightening it til it snug or loosening ?

what's the difference between tightening and loosening it ?
I haven't noticed any differences at all with tightening or loosening.

 

Fast Idle Thermo (FIT) valve should only have an impact on idle speed when engine is cold. It increases idle speed by allowing air to bypass throttle plate when engine is cold. It should close as engine warms to have no effect. If you tested on a warm engine, you would not see any affect of adjustment unless the FIT was leaking initially.

Improper adjustment would allow increased idle speed of a warm engine. As long as it's snug, it should seal when engine is warm.

good luck