Catalytic Converter whistle?

Maybe someone can help me out. I have a 2000 Jimmy 4d 4wd w/ a 4.3L. For some time now at idle I could hear what I presume to be the heat shield on the catalytic converter vibrate. Now the other day it got considerably worse and I noticed that going down the highway I could hear a high pitched wine or whistle closely resembling the sound of a turbo when I have my foot into the throttle. Once I remove my foot it goes away. Could this be from where the heat shield is welded or fastened to the catalytic converter? Any ideas or does anyone know what it would roughly cost to replace my converter? Lastly, it doesn't seem to affect the power it's just annoying to sit and listen to.

Maybe someone can help me out. I have a 2000 Jimmy 4d 4wd w/ a 4.3L. For some time now at idle I could hear what I presume to be the heat shield on the catalytic converter vibrate. Now the other day it got considerably worse and I noticed that going down the highway I could hear a high pitched wine or whistle closely resembling the sound of a turbo when I have my foot into the throttle. Once I remove my foot it goes away. Could this be from where the heat shield is welded or fastened to the catalytic converter? Any ideas or does anyone know what it would roughly cost to replace my converter? Lastly, it doesn't seem to affect the power it's just annoying to sit and listen to.

You sure no power problem? It ain't a plugged cat then;

Loose heat shield will make a sound at the same rpm EVERY TIME. But it's more of a fast rattle, that a whistle / whine...

There could be a hole in the cat causing it to whistle with your foot in the throttle. it may have something to do with the heat shield. I've never really looked closely at the heat shield but I would imagine it would be welded, at some point, to the cat. If the weld is broken it might cause a leak giving you a whistle at higher RPMs. If it isn't welded to the cat the shield may have, after smacking it so much, put a small hole in it giving you a whistle. If your sure you haven't lost power then that would be the next thing that I would check. If i'm wrong please let me know. I'm always looking to learn, even if it's something that I think I know about. Thanks and good luck.

Check the back pressure on it.
What is engine vacuum at idle and at 2K rpm.
For 80K or eight years it is under a federal emmision warranty and calf. may be more.
What is your mileage?

Just replaced mine. Cost was $250.00. Symptoms: loud rattle when car was running. I could tap on the converter and hear something loose inside. It appears that there is a substance inside the converter that holds the catalyst element in place and it had burned up, allowing the element to be loose. Muffler guy told me that more than likely I was running too rich or needed a tune-up which was causing the converter to get too hot. I suspect a leaking injection assembly under the plenum and that will be my next project. He said I had 15 days of warranty on the new CAT to fix the problem. You really can't permanently remove the CAT without affecting the drivability of the vehicle....as I wanted to do. Good luck.

Make sure the whistle isn't the fuel pump. Stand by your gas cap door and have someone turn the key to on without starting the engine and see if the whistle is heard during the fuel pump prime cycle. It only lasts for two seconds so listen carefully.