Try removing the valve and blowing air through both passages. If one feels restricted as though from carbon buildup you should clean it out.
AUTOZONE.COM
I own a 97 pickup with a ka24e and the vacuum diagram is right on the hood. But a local Nissan dealership should be able to print a copy of one from their service manual for you.
There are about 20 vacuum lines. Do you mean a main intake manifold line?
vacuum leak
buy a haynes book
get a webber carb idid it runs so good
haynes repair book at auto parts store or get a Nissan truck service manual,check eBay .the dealer wants 75.00.
That info is on pages 18 and 19 of the EF(Engine fuel) & EC(Emission control)section of the 1987 Nissan Truck/Pathfinder service manual.
Johnsautoparts.com
It depends on what engine. The hemi, does not.
You can find a one line vacuum diagram for 1997 Nissan 1.6 liter engine in the owner's manual. You can also find it at various auto stores.
I need a vacuum diagram for a 1987 suzu pickup 2.5 lt engine