Yet ANOTHER weird problem with my 07 tls. On cold starts, not necessarily real cold weather, but cool engine, my engine make a very loud putting or pulsating sound which goes away as the engine warms up. I think it's an exhaust leak at the rear cat connected to the manifold. Anybody ever have a leak there? Any other ideas of what the noise is? Note, the sound increases with higher revs.

 

I have the same noise at start up.
Goes away after 20 - 30 seconds.
Then I started hearing it when I was driving.
After a few weeks of I figured out I also have a cracked precat that is on the front end of the car.
What is wierd is that the sound at start up comes from the same area as the defective precat.

 

did you end up replacing the precat to solve the problem?

 

It's on order.
I ordered the RV-6 High Flow Pre Cat with ceramic coating that is going to take about 2 - 3 weeks from what the site said.
I dieing to get it on.

 

good idea. i was thinking of getting the pre cat deletes. if that doesnt solve the problem, oh well, i got some good sound to cover it up

 

I was going to get the PCD but I just do not want to deal with the strong exhaust smell.