the shaking at startup could be bad or incorrectly installed o2s. theyre very sensitive so if you bumped them or dropped them, they could be broken. pre-cat o2s help regulate afrs, without them your car wont be happy at all, esp when its not warmed up. Its not a critical failure like a water pump, but you want to get it taken care of.
E88 FBO N54 Alpinweiss/Coral Red/Meisterschaft Race/Berk Resonated/Macht Schnell 3"/ER CP/Synapse/VRSF FMIC/FFTEC LPFP/HFS-4 DO Stainless Lines/BMS DCI/BMS Thermostat Delete/Rob Beck PCV Valve + Cap/BMS OCC/Cobb E60/ST Coilovers/M3 Front Control Arms + Tension Rods/M3 Subframe Bushings/Apex ARC-8/Project Kics/Macht Schnell Studs/Rogue Transmission Mounts/Alpina TCU Flash/Icarbon/Kerscher/BMW Performance/Cyba