Post 2000 has a slightly different dash display. There are other differences also. I know that the 01 has head curtain air bags and the 99 does not. I don't know about the 00.

I've had no problems w/ my 01 4matic.
My 91 4matic has been somewhat troublesome, but is still operational, original, and excellent at 207,000 miles.

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07 E350 4Matic wagon, 06 S430 4Matic, 99 SLK 230
retired W210 (x3), W124, W126