Rusty wrote:

As you may recall, I tried using a fuel filter and a needle valve to smooth out my idle, with absolutely no success.  I've had a normal vacuum gauge on the line before, and never saw any significant bouncing

One of the things I concluded fooling around with the MAP filtering was that it seemed to need about 3 cu. in. of volume (line plus filter, or whatever) to act as an effective “spring”.  Have you estimated how much volume you have?

Al