HO plenum MTV vavle
I think that's what it's called.
the electronic switch that open the butterfly valves at 5000rpm.
When its sub freezing the mechanism doesn't work properly when downshifting from 4 to 2, it pops open around 5800rpm instead of 5000 (the initial engine speed when it enters 2nd).
From a dead stop in 1st it opens up and 2nd as well. Seems to only happen during downshifting and in cold weather. And I can hear this due to the K&N FIPK, and feel the surge in power at 5800rpm when the valves do open.
Any ideas, the car was not originally an HO, now running 04 special PCM. Haven't had an issue since it got real cold.