probably either spark plugs, spark plug boots or ignition coil, could also be maf, fuel injector/pressure regulator or a blocked cat. it is possible that its o2 sensors, but they alone wouldn't cause misfiring as bad as you describe.
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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