[v3.2mc]

It's been a little while, but if memory serves the differences are due to...

1) the N52 had some pretty serious issues with the CVV freezing in cold climates. the N52K design changes helped, but did not completely solve that problem.

2) the N52 valve covers leaked constantly, so a change in valve cover design was introduced to help with that. it solved most of the issues, but the N52K is still known to leak.

but the biggest reason...

3) the N52 sounds like a diesel engine when it's cold out. BMW was pretty desperate to try and fix this issue as they were replacing cylinder heads on thousands upon thousands of cars under warranty due to customer complaint (3's, 5's, X3's, Z4's... you name it). the list you show above covers some of the changes they tried before settling that the original cause was a lack of anti-flowback valve in the head (which the N52K has). basically, the N52 "lifter noise" is due to the car sitting in the cold. the hot and thin engine oil would easily drain out of the head, then upon cold start (usually the next morning) the valve train would be "dry" (not really... just using this word for effect). without sufficient oil, the lifters make a hell of a racket. eventually, BMW no longer put heads on cars, and instead would just pay for new lifters. the tapping noise always comes back though. however; there are some (myself included), that have moved to 0W-40 in their N52's and it does help (though very cold days still produce the loud rattle).

it should be noted that my 2006 325xit has 174k miles on it with original head and lifters and no failure of any type. yes the valve cover gaskets have been changed a few times, as has the CCV, but the internals have been solid. the noise is just noise... a mere annoyance on super cold days... and nothing to be scared of. there is an updated CCV system was available at one time that had the installer hardwire in a heating element or two around new fully insulated CCV drain hoses, but I'm unsure if that's still available.

edit: NOTE! the N52K still has lifter noise when it's cold out. it's not as bad as the N52, but it is still there.