An E90 330d has no real issues so if it looks right, drives right, pulls well chances are your on a winner, .if any dashboard warning lights are on they are expensive to put right, a passanger airbag ECU costs £850, ABS pumps and moduals are common so watch for ABS or DSC lights on, body control moduals when failing do weird stuff so make sure central locking works on all doors and boot, both keys operate the locking and start the car and just make sure it all works as it should, dashboard has all instruments illuminated, instrument cluster should all light up and do no weird stuff, in short electrical failings are the biggest pain in the ##### and something that appears to be very little can be mega expensive to sort, just use your eyes and ears and am sure you will be fine, REMEMBER to HPI the car check the paperwork (V5, MOT, servicebook etc) and let me know what you think if you buy it, they are a great car, great performance and great on the juice when driven with respect. Stephen