On first (cold) start I get a very high pitched buzz or whine that seems to be coming from the EGR shutoff valve on my 1997 E320. Although it could be coming from another location, it's loudest on the valve (listening through a stethoscope). The part number stamped on the valve is A002 140 25 60.

The buzz lasts for about 60-70 seconds, then the engine goes into a normal idle and everything sounds and runs fine. There is no check engine light, and the engine runs and idles smoothly when warm.

The buzz can sometimes be loud (maybe a ripped diaphragm/vacuum vibration type noise--if that makes sense?).

I'm wondering if this is an issue anyone has come across before, and if there is anything a DIYer can service/rebuild in respects to the valve. The new part lists for $404 (and I'm not inclined to shotgun parts at the issue until I can figure out what the latent problem is).

Thanks for any info.