Sorry I can't help you with the EGR question on the 87 3.0 liter diesel, but I noticed in your post that you replaced the diaphram in your shut-off valve to eliminate "dieseling".
I am experiencing "dieseling" with my 87 300 wagon and have a current post titled "vacuum lines". The dealer claims they "cleaned" my vacuum lines and it worked for a few thousand mile but is now running on again. Was it difficult to replace the diaphram, and how did you do it?
If I pick up any info on EGR valve bypassing on 87's, I will let you know.
Thanks, John

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83 300TD wagon
87 300TD wagon
89 BMW 325IX