rattling/drum like noise and few other quirks

[BMW X5]

this was possibly asked/addressed but wanted a fresh set of ideas:

2013 35i with m-perf pack (not sure it matters). on cold starts somewhere in middle to front there is a metallic rattling/metal plate hitting noise. have heard that this sometimes relates to the waste gate but have had the dealer "address" it multiple times with no success. the last time they replaced a "malfunctioning mechanical exhaust flap" to get rid of noise (maybe it was actually bad but noise definitely was not from that). The lease is up in a few months and I'm at a crossroads of keep or not so not sure how to get them to address this. Can't imagine this is "normal" since every other x5 I've driven/been next to sounded normal. I did get a loaner 5 series which exhibited the same behavior but again cannot imagine this to be normal.

the other 2 issues have to do with fuel gauge not reading full when the tank is actually full (the last time dealer reset the battery and "issue resolved") but this is non-sense and after the first empty to full fill-up issue returned.

last issue is when on decline the low oil notice comes up but when on flat surface it shows oil level is full have not had this addressed yet and worried about adding more oil if it is in fact full.