Hi everyone, I registered after reading this thread.
I purchased an approved used 320si last year, 2006 with 38k miles on the clock.
After advice from this thread I sent it to the dealership for a valve clearance adjustment at 40k miles (and had an oil/filter change). During the inspection they found the rear diff's leaking so the seals were changed as part of the warranty. Also they found a problem with the fuel filter (after I reported a whine in the engine). That is also getting changed under warranty.
Currently I am on 41k miles, going soon on 42 and I must say it runs really well, I can only hope it continues.
cheers