Vibration and drumming sound

[2chronicles]

Hi 2-3 months ago had a replacement cat fitted to 02 406 estate , by "you cant get better than a...etc" well I am sure you can! Ever since then when running at 20,000 revs (the car engine I mean)both mobile and stationary there is a vibration through the car and a drumming sound. I have been back 6 times they refitted it 3 times ,replaced the cat .
and then suggested it may be a faulty an engine mount which seems coincedental as the sound only appeared after they had their mitts on it!
Any suggestions as its not doing my blood pressure any good!

[steve_earwig]

They've put the wrong cat on it? Maybe one without a flexible section...

*resists urge to comment on screaming engine*

[jasper5]

Put on some gloves, go to the back of the car, get hold of the exhaust and shake it or bang it, sideways.If you can hear the noise, it's definitely something wrong on, or in, the exhaust.

[steve_earwig]

That's a point, could be they put it on pi$$ed and it's vibrating on the body. You can't get thicker than a...