There will always be issues, but stock 335's seem to be about average for maintenance. People who mod theirs have had relatively few issues for what can be expected on a turbo car.
If you can't swing a wrench, mabye CPO is worth it. If you can, it almost certainly is not, unless you dont know how to buy a car and end up with a dud.
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2002 TiAg M3 6mt
deoranged, dechromed, led tails, ZHP knob, UUC SS v3, GROM, OEM 220M 19's, Michelin Supersports
2006 YZF-R6, bunch of go-fast stuff