I just picked up my 2005 Sedan a week ago. I noticed something the other day that doesn't sound like it is normal. When I'm cruising at 60 MPH ~ 2100 RPM, then moderately accelerate to about 2700 RPM and let off the gas and drop back down to like 2400 RPM or so I get a high pitched annoying howl/whistle coming from the front left of my car. I was wondering if this is normal. This seems to happen at other speeds but is most noticeable on the highway. The only infiniti dealer is like 35 mins from my house so I wanted to check with you guys first. Thanks in advance.

Do you have a Z-tube? I noticed that once I put my Z-tube with K&N filter in, I get a very high pitched noise that is a direct relationship to my foot hitting the accelerator/gas pedal. I believe it is the air intake noise. I don't find it annoying..kinda neat actually. Front/left side of engine makes me think this is definitely what is happening, as that's where the intake/tube is!

I get the same noise from my z-tube.. If you have a z-tube I think it's normal.

It's normal, period. Both my 04 5AT and 05 6MT exhibited this sound stock. It's the intake.

I didn't notice this sound until I put the Z Tube and K&N filter in and I didn't drop it in until my car had 46k on it. Now, every time I hit the gas...between 2700 to 4k I get the whistle. I was told that the K&N is causing it...so I'll double check later. Let me know if anyone else is getting the whistle even without the K&N.

As far as I know, my intake is stock. I did change my air filter. I used a STP replacement from AutoZone. I can't remember if it made that noise with the stock air filter since I only had the car for a short while. Maybe I should try an OEM air filter. Thanks again.

so it started after you changed the air filter?? its the air filter, double check the air box and make shure all the little clamps are where they are supposed to go

I don't recall if it made that noise prior to changing the air filter. I only had the car a day or so before I changed it. I'll double check the clamps though. Thanks

I had the same kind of noise with my Stillen intake at certain rpm.
I liked it so I got the SC and now I when I am on it I can annoy people 3 lanes over!