I just got a Dinan High Flow Cold Air Intake installed on my 2001 330Ci yesterday (with the Stage 2 Engine Software and the Automatic Transmission Performance Software, as well). I really love the difference in acceleration/sound. However, I noticed that there is a kind of a whistle or a whining sound that happens sometimes when I'm already going a good speed, and just have my foot on the gas to maintain the speed. Of course, there's the sucking sound that happens when you punch it, or really give it gas, but that is just the intake taking in the air, and I know that's normal.
Is it normal for the more constant whistling/whining sound when just driving at a constant speed? It doesn't do it the whole time, but it will do it for quite a while, unless I adjust the gas I'm giving it. With the windows closed, I can't hear it, only with the windows open.
Any advice? Thanks in advance!