So I finally get to pick up my car on Thursday, after it going in for a sensor change on the 9th May... Yep, you heard that right, 2 months and 18 days at the dealer. Granted, about a month of this is due to the dealer being absolute dog****e and taking forever to get to even start work on the car and going back and forth with AMG HQ, but I thought I'd share some info as it may be helpful to other owners experiencing the issue. So a month or so before this saga, I noticed the car being ever so slightly rougher on idle and on random and rare occasions the right bank would misfire (Error codes would show cylinder 6,7,8 + multiple random misfires detected). As you'd expect, I thought this was due to the plugs and had them changed along with a major service shortly after. The car felt better but not perfect and then started to display 'Camshaft Sensor position error' the day after. I called Mercedes, had the sensor replaced which worked for a day or so before it came back and went straight back to the dealer. Long story short, this went all the way down the line - having sensor, solenoid and camshaft replaced before determining that the chains had stretched. (Not sure if they should have been determined beforehand - but the classic dealer line is "we have to go down the line to determine what is wrong rather than starting at the deep end" - even though it's kind of common knowledge that the chains are the weak part of this engine). Anyway, the important part, the chains that have been replaced are a new part from the factory which comes with chain guides and uprated links (the previous part were just chains and used the guides already on the block). Mines all fixed now with no issues and running smoother than ever, but thought I'd give owners and future potential owners a heads up. The car has 35k on the engine, I've owned it since 8k and it always allowed to warm up, kept under 1.5rpm until temperate reaches 80, serviced regularly, only ran on Vpower and spends most of its life at a 70mph cruise on the motorway down to London and Oxford. So, I guess this could really happen to anyone.