I just purchased Bosch 4417 Platinum 4 electrode plugs. $25 for a set of 6 with free shipping.
I'll post back with results, but I'm sure anything would be an improvement. I scoured through my service records and could find no record of plugs being replaced and it is definitely feeling sluggish lately. 96k miles.
NEW BMW SPARK PLUGS BOSCH PLATINUM+4 FACTORY HIGH POWER 6PC SET E39/E46-M54 4417 | eBay