hi all i have had a rattle from under my car for a few weeks now the sound was coming from under the front passenger seat where the cat sits so i thought it was the cat breaking up any way yesterday i replaced the cat for a new one guess what the exact same noise is still there . i thought it was strange because when i removed the old one i gave it a good shake and it never made a sound i would of expected it to rattle but no .i have checked the heat sheild above the cat and it seems solid the car as covered 114000 miles and is still on the original exhaust if it was another box in the system that had the rattle do think the noise could travel to the ceramic honeycomb in the cat because the noise is 100% coming from under the passenger seat where the cat lives dont you just hate it when you replace a part that does not solve the problem . as anybody had this problem any info would be helpful