While Claudio is absolutely correct (one more Karma!) regarding the baffles negatively impacting the wave form, this can be overcome, although it may require some mechanical effort.
Many times, these "adjustable" runners can be rendered inert bu simply disconnecting the vacuum line and plugging it. This MAY cause a MIL, it probably will not. But once the baffles inside that allow the adjustment are rendered static you have a 50/50 chance of seeing the gains you're looking for.
Karl, why do you gravitate toward these exotic systems?
"Gimme that OLD-TIMEY engine, gimme that OLD-TIMEY engine, gimme that OLD-TIMEY engine! They're good enough for ME!!!"
Ron