Put a filter on shut off vacuum line

[kerry]

I recently discovered that despite the fact that the engine shuts down fine the shut off diaphragm was leaking oil. It has made me think we should put a clear filter in our brown shut off vacuum lines so that oil leaks into the vacuum system are visible. I had assumed that a diaphragm with a hole in it would manifest with poor/no shutdown so oil leaks would be readily detected. Apparently not so.
I haven't found an appropriate filter to go in the line but I will look for one when I next visit an auto parts store.