Cold start rattle

[M-A8]

I've had this issue for a while.
Every time, or at least most of the time after car been standing for 10-12+ hours I was getting a gentle (nothing super loud) knock from under the bonnet. It always lasted no more than 2 seconds and if you switch the engine off straight away and start it again the noise wouldn't come back until next morning (this is before and after replacing chain tensioners-read below).

After several days of investigating the problem I have narrowed it down to chain tensioners at the back of the engine, one per side. In fact one of the was slightly seized so I've decided just to replace both of them for the sake of it.

To my surprise I was still getting some knocking/rattling noise, but slightly different quieter, but still noticeable for my an@l ear.

I've checked all the possible parts which could make this noise over the weeks as I could only do one test a day, in the morning.

In the meantime I have a found document released by Audi here on the forum, I'm pretty sure it was in the D2 section, listing all the engine which can develop or have this specific noise, but. There was a lot of V8 listed but the my BFL engine wasn't on this list so I called my mates who both are ex Audi master technicians and the last thing which could caused this such noise where non returning oil valves under the intake manifold, so I went to Audi and ordered both valves, bot manifold seals and the seal plate.

Approximately 2.5hours later job was done, but I wasn't convinced this will sort the problem purely because the valves I have removed seemed to be fully working

In the meantime, I wanted to take the manifold apart and just see the condition of it and how the exhaust manifold flaps are working and I was shocked when I saw all 4 little torx screws loose, one really badly and all other 1/3-1/2 out. I've tighten them up to the recommended Nm setting and I putted all back together. For a second I thought that this is what is causing the noise, but I've been reassured over the phone by Audi guy that this wouldn't cause this noise.

You will see 3 photos there for manifold flaps, 1st the closed position, 2nd one with one open (approx 3000rpm) and 3rd one with the other one open at around 4000rpm up.

I'm not sure if I should be impressed, but the intakes and valves (top) were nice and clean as per last two photos.

So all the parts were about £100.
I've replaced both intake seals, both valves and the seal plate, all info to what Nm you need to tighten the valves, plate and manifold bolts can be found in the D3 Tech Dump section thanks to Del

All whats left was to wait till the morning and start the engine. I've allowed 18h this time before starting the engine next day.

The noise was still there the next day but since then I haven't heard nothing, well I think I heard something two/three days later, but I wouldn't be surprised if that was my mind playing games with me and me looking for a problem again and for more things to change.

Anyway, if I'm honest, I can't say for sure that this was the problem. All I know is that there is no noise anymore and it all runs nice and how it should.