The 99-01 models are all the same as far as I know, in 2002-2003, the front bumper and rear bumpers were given a facelift (mostly front), and in 2004, the headlights and corners became more swept back, mainly the bottom left of both corners are now cut off... Kinda hard to explain w/o pics.
Also, in 99-00 the model #s were 323 and 328, in 01-04 the #s are 325 and 330. Somewhere in there was an e46 318, but i dont know when, and now there are 320s but not in the US.
This is pretty much the extent of my knowledge for changes in the e46.
Oh and in 2004, Alcantar interiors were introduced, + the M-sport stuff was added onto 330 ZHPs.
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