I'ts been happening for a few weeks now, only noticed it at cold temps, but now its happening at running temp.
Basically, when letting off the accl to slow down, the engine starts to make a whistling noise, and will continue while at idle. The noise stops when I rev the engine slightly, and begins again when I left off the accl.
When getting up to speed, the noise isn't noticed except during shifts , then begins any time I let off the accl.
Does not make any noise at cruise speed.
I replaced the air filter when i first noticed it, but made no change.
I've looked for loose or broken vacc. lines, but I don't see any.