[RarlyL8]

What is this engine noise?

At least that's the question I didn't think I'd ever have to or want to ask.
I purchased a 2001 996 right at one year ago with 89K miles on the clock to do some R&D for my line of exhaust systems. My wife latched onto the car immediately and never let go. We both just love it. It has a tip trans so she can drive it easy in the hills and mountains where we live. Car is driven easy by us both and now has 92K on the clock.
I drove my daughter to work yesterday, came home and parked the car, loaded up a couple boxes to run to FedEx and then hit the key to start it. Car started quick then died. Very odd. Hit the key again, same thing. Cracked the throttle and hit the key and it stayed running but had a fairly loud metallic clicking noise out the exhaust that followed engine RPM. I let it run for several seconds to really listen to this sound then shut it off. No warning lights came on during this time.
I have a hunch what it MIGHT be but would like to see what you guys who have owned these cars longer think. In all my decades of owning air cooled Porsches I've never had an engine failure. I thought the world of this car until today. It had become my favorite to drive, even took it on a 1000 mile trip a few months back.
The noise is different this morning. A lot less noise and not as melodic in following the engine RPM.
Here is a video, what do you think?