(Recently) noisy 996 turbo ? chain/IMS rattle

Increasingly noisy 2002 911 996 Turbo (X50) engine - 78908 miles - thoughts/suggestions...? I bought my son's lovely 996 Turbo two years ago (to help finance his purchase of an equally beautiful 2005 997 GT3). Never a 'quiet" engine, I think (in retrospect) that it has become progressively more 'rattly" over the past six weeks or so (my wife is certain that it sounded normal on 31 August). It is a bit grumpy at idle (as usual) but runs beautifully smoothly with no change in the (sparkling) performance. Oil and coolant levels are stable, oil pressure likewise. We took it to a local IPS who removed the auxiliary belt (noise unchanged), checked the oil filter (clean,no swarf) and could find no obvious, simple mechanical cause on thorough inspection up on the ramp. The car was inherited by my son in 2012 with approx.150 activations in Rev Range 2 on Durametric analysis (the last well over 100 driving hours previously) which increased to 230 without any history of mis-shift several years ago. An Independent Porsche Specialist (IPS) suspected a throttle potentiometer fault but it then remained stable at 230 until January 2022 when it increased to 283. No mis-shift but possible red-line when I braked and disengaged the clutch in hard low gear acceleration (a car pulled out in front of me) and the clutch was subsequently re-engaged to overtake when clear to do so (in the same gear). The car was taken to another IPS for replacement of a failed rear spoiler ramp at the end of July (10-12 hour return journey) following which Durametric showed Rev 2 range increase to 359 (now 66 driving hours ago). I can recall no mis-shift or other sudden over-rev on the way there or back and neither did the mechanic (who did road test the car to investigate recurrent emission fault codes). The car has been serviced during our ownerships by OPC Bournemouth and Nine Excellence (IPS Horley). Last oil change (Mobil 1 0W40) OPC 08/21. Minor service and suspension work 9E 06/22 and engine sounding normal then and when MAF sensor changed at IPS (recurrent emission fault codes) on 6/08/22. The engine sounds (to both me and my son) normal when started cold but becomes noisy as soon as it starts to warm up. The rattle appears less obvious with increased throttle (but ? just obscured by engine/exhaust noise) and transiently disappears as torque is taken up when moving away from stationary. The threads on various fora, including this one and those on which the helpful local IPS mechanic has been researching, have videos of and comments on rattly Metzger engines with suggestions ranging from 'try changing to a higher viscosity oil" to 'engine re-build required" (and one 'it's toast"). I am a mechanically illiterate retired NHS quack whose first car (age 18) was a Lotus Elan S4 S/E roadster (built from kit form, complete with L plates) who had hoped to see out his driving days in this enchanting old 996, 'Freyja". My local IPS cannot make a concrete diagnosis after inspection and is hesitant to suggest proceeding to full engine strip-down +/- rebuild as the ? inevitable next step. Noting an entry on one forum from an acknowledged 996 turbo specialist who had rebuilt an engine for a worried customer only to find that it sounded exactly the same afterwards, so am I!. I attach videos of the car upon starting and once warm. Any thoughts/stories/advice very welcome. At start-up (cold): https://youtu.be/e7wojhDXR6E Warmed up: https://youtu.be/0VbyivdsKo4

They do vary in the amount of noise they make, the cold vid sounds just like mine, the warm vid is a fair bit louder. As always it's hard to tell from a vid. With out trying to alarm you too much there is one thing which can go wrong with the turbo engine which is the bolts which hold the cog onto the intermediate shaft can come loose. Most cases of this that I've read about cause the usual noise to get much louder over a relatively short time as the bolts undo. If this is left the bolts can fall out and get caught in the chain or teeth and ultimately cause engine failure. I'm not saying this is what yours is doing but you do think the level of noise has increased over a relatively short time so I think it would be prudent to get an expert on these engines such as Ken at 9E to check it out. People who have had it happen say it gets loud enough for people you drive past to comment on the noise which is not the case with the usual chain noise made by most turbos. If you feel that yours is that loud I wouldn't drive it until and expert listens to it. If this fault is caught early the bill to repair is not that bad, if it progresses until a bolt comes out it it is horrific! Hope i haven't scared you but definitely worth knowing about Mac

If the car has been tuned and rev limit raised to 7200rpm it will register an over rev every time you go past 6750rpm. Doesn't sound terminal to me tbh and if you want a second opinion for peace of mind take it to someone like Sid at Porsche Torque or Steve at Jazz. Some engines are louder than others and 996/997.1 turbo has a hand built race derived engine. Very unlikely anything untoward has happened to it but no harm getting a second opinion.