My Trial exhaust has recently been making really loud rattling noises when the car is started up. I was thinking about getting a replacement but Trial is making me pay shipping to and from Japan so Im gonna try some other tests to see what the problem is. I checked all the nuts and bolts including the hook mounts and everything is tight so I'm sure it's not caused by any of that. I asked my brother about and he said that it is because of back presurre on the cat. It's strange because after I drive for a little while it stops. Has anyone had any experiences with this?