Bernard---At the end of your interesting message on EFI's you asked if
open exhausts change the vacuum signal by much. I have the option of
running an open exhaust quickly, by opening a two bolt flanged cap,
which then bi-passes the muffler. At idle, there is no indication of
higher vacuum with the exhaust uncapped. (Mine's steady at 20 inches.)
Perhaps if the muffler were more restrictive it might. The benefit, if
any, would be at higher rpm's when back pressure might show up. I think
the comfort level and what one likes to hear coming from the exhaust
pipes should be given the most weight here. Kastner's comp prep book may
confuse those who like the twin pipe theory. At least it did me.
Dick T.
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