i have a stillen y-pipe and when i gas the car half way to the floor or do a turn i get a loud rattle sound... it comes and goes.. i didn't see the pipe hitting anything so what could it be? anyone else have this problem? it sounds like its hititng the shifter on the automagic.. hmmmm
it is not the bees in a can sound.

 

Aside from the actual y-pipe banging into something...

Check the upper heatshield above the catalytic... sometimes the edges start touching the body of the car and may vibrate.

Also check the heatshield on the catalytic converter too... A weld may have broken or there may be rocks stuck between..

GOOD HUNTING!

 

I have a SS Cattman y-pipe and have the same problem when I accelerate. The rattling begins around 4,000 rpms and only lasts a second or two. I have to get under the car and see what the hell is causing the rattles.
Let us know how you make out wicked
Thanks for the tip Chunger

 

Give it a couple of days. The flex pipe is well flexing to the shape that it will be for the rest of its.......life. It will do that if you are going fast over bumps but after a day or 2 it will be gone.

Chris