I get a whistle at about 4,000 RPM.
I've been told it's a bad diffuser in the muffler (stock)
Any ideas?
Thanks

It's normal to about 90% of 2gnt's. I even get it with the exhaust i have from a gs-t which only had about 20k miles on it. Pretty sure it's the Throttle body. I would just ignore it!

Probably a bad bearing in your AC/PS belt pulley. I have it too and that's what it is.

aaron that's more of a high pitched squeely sound. Usually makes that noise more in a load situation. If your taking a turn and create load on the bearing then it squeels, that's what mine does anyway. So I took off the belt run no PS/AC and it still whistles like crazy.

See that's odd because no matter what I do to the intake line it's the same sound (used to have a CAI and 57mm TB). Sound goes away when I took off the PS/AC belt.

i get a whistle at 4000 too and i have an aftermarket intake throttle body and exhaust, but it makes my car sound turboed so i dont care, i really dont think its a problem, unless of coarse the whistle is a squeel like mentioned earlier than id fix that.

my car used to get that whistle too at 4K rpms when i had my CAI. Once i got a turbo it went away.

Yea i have a strange noise too at 4000-4800 rpms. It seems when the car heats up it will go away a little. Not sure why. :shrugIm hoping the turbo will take car of it.

it's totally normal. ignore it with reckless abandon.

it's your exhaust, mine has been whistling for a looong time now.



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the first solution that comes to mind for any new problem with my car usually involves a can of gas and a match.....:wallbash

Mine does it too. I kind of dig it. It is real high pitched and almost unnoticable unless its real quiet in the cabin. It whistled when my car was stock back in 98. It remains unchanged now with a CAI, bored TB, P&P intake mani, header, hi flow cat, catback, and all new silicone vacuum hoses. So I rule out all the above guesses. It could, however, be the pulley that Aaron refers to.

i know what it is . take your heat sheild off your exhaust manifold and look right in the middle on top and you WILL see one or more cracks in it. i think ive only seen one in my life that wasn't cracked and they definatly wistle after 4 grand.

nope, I have a header and it still whistles.

I was expecting this to be a Bubb Rubb thread. If you know what I am referring to, you are truly old school.