4" usually no rattles.
My 5 inch was touching the firewall heat pad, the cross member and the spare tire heat shield.
I loosened and rotated the downpipe to avoid that heat pad.
In doing so it moved the pipe 1/2" away from the cross member and used a crowbar to bend the living crap out of that spare tire heat shield.
No vibes after that. Hope that helps.
Bookmarks