ever since i got my 01 cls, i always had a engine whine from my car when its at idle. I know i do not have the comptech icebox, so i was wondering is that normal. Its coming from my stock air box i think.

 

I just developed the same problem as you and figured out what was causing the whine. I took my car to Jiffy Lube for an oil change, and the next day I noticed the noise. I opened the hood with the engine running and noticed that one of the retaining clips on the air box was broken. When I pushed the cover down on the box, the sound was much quieter. The bastards broke my air box! Oh well, good excuse to upgrade to the icebox. To answer you question, the noise is normal, but you may be having the same problem as me with the broken clip.

 

You shouldn't hear a whine from your engine. I don't care what people say. It's not a normal sound unless you have a turbo. With that said, I recently had a icebox installed (incorrectly). The car was making this crazy whine. It turned out to be a bent hose. I repaired it myself and now its super quiet again.

So I would say check for:
-possible air leaks
-air restrictions (sharp corners)
-loose parts

 

I took my car back to Jiffy Lube today. Turns out they reinstalled the air filter incorrectly, so I don't know if they broke the clip to begin with or not, but the whine is gone. Problem solved! I ordered my icebox today anyway, reading about all these modded CLs is making me jealous. More power on the way!

 

i have that whine too but i guess ive taken a liking to it..