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Discussion Starter · #1 ·
I cruise at about 3k rpm
Issue is at lower rpm highway cruise vacuum will be higher . but the higher the rpm i cruise the lower it gets . its cruising around 11-9 Hg vac and i should be seeing about 15 i would assume.

the sig below are my current mods. Could this be exhaust restrictions or something. I can't find any vac leaks.
 

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15-17 is normal at idle I would say unless you suspect a vacuum leak your right in the norm. If your really worried about it you could try spraying carb cleaner all around your intake at idle and look for a differrnce in rpms

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15-17 at idle is low. More like 20-22. Cruising, all depends how much throttle effort your giving it
 

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Ive seen it range. does your car have any drivability issues like a rough idle? Or poor gas millage?

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Itll be low if you have cams, high DA, or leaking rings
 

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My gauge has always read 18 in.hg. at idle. For about the last year it has said 16 but when I tap the gauge it drops back down to 18. The needle sticks.

All cars have less vacuum when cruising than they do at idle. The only way to maintain 3000 rpm is to have the throttle open a little. The more air that gets in the less vacuum you have. I don't remember what my reads at 3000 rpms. But looking at the data in your post, I'm not sure you have a problem.
 

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I don't think you have a problem. Thats about what I cruise at.


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Discussion Starter · #8 ·
makes sense. at around 60 mph it will be at 15 hg. Before the supercharger was on there and just the cams 3k rpm would give 15hg . i guess the supercharger is keeping the engine with extra air and throwing it off or is it possibly a BOV thats too small ?
 

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Discussion Starter · #9 ·
Man stuff gets moved back in this forum fast
 
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