There was a post by ECS Tuning piped in one of the oil separator threads I found recently with a link to a special shopping cart for the cold weather bits; I got the following list from there:

11617533400 Pressure regulating valve, Cold Climate Version
11617533398 Vent Pipe
11617533399 Connecting Line
11157532628 Vent Hose
11727545323 Vacuum Hose
11617504536 Return Pipe

I think the price through ECS was about $150. I also got pricing from Steve at BluntTech.com (BluntTech is a Minneapolis company) and it was about the same. I put off the purchase when I found that the previous owner had it all replaced less than a year ago. May still end up doing this job, depending on what happens with oil consumption.

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2001 X5 Sport 3.0/5-speed
1998 318ti/5-speed
1988 735i/5-speed
1984 528e/5-speed (soon to be M20B25-powered 525i!)