I was at my BMW dealer some time back and we were talking about the 540 and he said there was a major engine change- *I think* from 99 to 00. It had to do with the cylinder sleeves(?) and was changed due to recall issues of prior models. Can anyone fill in the blanks here please.

I'm looking to buy a 540 and just starting to get educated.

Any other tips on the different 540 models much appreciated.
Thanks!