Exhaust noise.
 

I have a 2001 boxster with 100,000 miles on it. I have noticed a rattle the last 1000 miles which appears to be coming from the right side warm-up catalytic converter. I mostly here it when a low rpm's. I noticed it gets louder when the engine is warmed up to normal operating temps. It sometimes seams to be accompanied by an exhaust leak type noise when I let up on the gas. Any ideas of what this could be would be greatly appreciated.

exhaust noise
 

First off congrats for those high mileage. Have you tried raising the car yet? could be just one of those heat shields rattling , or can also be some lose hangers or rusted bolts from the exhaust..
i'm sure this one should'nt be too hard to diagose..
good luck

I had noticed something similar on my 2000 Boxster with about 90,000 on it. I had it checked out, and the only thing wrong was that one or more baffles inside the rear cats was coming adrift.

It only shows up at a couple of rpm points under light throttle. I'm going to try a secondary cat delete and see if that addresses it. If I'm wrong, well, there really is no downside but I'll look at the exhaust afterwards.

I did raise the car, and there was some heat shield rattling contributing to the noise, but the main rattle is still there. Thanks for the idea.

Let me know your results. That does make sense. My rattling cat is connected to the exhaust manifold.