Why not just put a couple of golf tees in the line to cut off the EGR? It is not needed and could help with your vac leak problem. Although I am really a purist and try to keep my '81 SD completely stock, I did this years ago and have never seen a problem from having no EGR.

Pic of mine showing one of two (as I remember) golf tees. The white one is easy to see; I think another is very dark at the bottom of the pic.

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