I took our X5 to get smogged last week, the technician called me out after about 5 minutes and said they hadn't tested it because it wouldn't pass anyway because of the burning oil. I didn't even realize it was burning oil. He said on V8 X5's they always let them idle for a few minutes to let the oil buildup and then when he blipped the throttle sure enough, there's the blue smoke.

On the advice of a BMW mechanic friend I replaced both pressure regulator valves. Kind of a long shot but they are cheap and easy to replace. I couldn't tell if they were bad or not but they did fall apart when I removed them. Unfortunately that didn't help so I've ordered new seals and spark plugs and will tackle that job this weekend.

I'm not one for step-by-step DIY's but like with my rear diff repair I will update this with general steps and some details of more difficult steps.

Wish me luck!