I looked your car up in my ETK software and BMW recomends a Bosch W8DC. Its what came in the engine from the factory. I use factory Bosch bosch plugs in my 2 BMW's, '81 320i and '89 325i, and have had no problems. Unless you have tons of engine mods all you need to use is factory recomened plugs.
Just noticed you live in Sac, I live up in Lincoln. I'm going to the ALMS race tomorrow at Sears Point if you want to follow me down there. I'll be leaving early, arround 7am and should be going throung Sac arround 7:30am.