High idle?
between coolant loop and air path.
However, the bypass is often done at the time you
port the TB, and -that- can result in bypass air leakage
if you mung the blade or its seating circle.
Sometimes people jack with the setscrew to deal with
low-idle issues and then when it's fixed the right way
the idle is stuck high.
PCV plumbing includes some soft bits that can tear
and leak air.
Think "vacuum leak".



