Before you start modifying parts, I would consider doing two things:Morning, I have checked YouTube and asked several experts. I have no idea why the clearances would be so close, but I think I will try to machine a bit off of the top of a the four buckets. To take the head off and machine the valve stems seems just as bad as machining a bucket. I wish I knew if the valve clearances have every been checked before. I am sure of my clearance checks so we'll see I guess. .10 mm is a very small amount.
1. Check with a different set of feeler gauges as it may be you have a set that was stamped incorrectly or something.
2. Try to find someone else to check your clearances.
Anything is possible, but the likelihood that BMW made a head with every valve seat ground too deep is quite unlikely. Unless this engine has 300,000 hard miles on it, it is very unlikely that the seats have worn this much. No offense, but some of your earlier responses really make me think you aren’t familiar with checking valve clearances and likely are doing something fundamentally wrong. I would want to really, really be sure the clearances are this far off of normal before I start machining parts and likely messing them up and causing real serious problems.