Alternate vacuum source

[michael glidewell]

My 528i (1981) manifold vacuum is around 13 in Hg, reasaonbly steady, for an
engine with 168k miles. I beleive the vacuum should be higher, based on
Haynes manual, say around 16-22 inches. Question is, am I getting the full
distributer advance with a less vacuum? I think not. Maybe a separate vacuum
source which is controlled by the manifold vacuum could improve eng
peformance. Anybody been tried this or have some thoughts on feasability?
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Michael Glidewell       Boston, Massachusetts	glide at shore.net
KE1CP     BMW 528i      BMWCCA 		http://www.shore.net/~glide/