Indentify small hose on top of intake manifold on a 1998 3.3 nissan pathfinder engine

Question edited for clarity.
Question moved to model category.

There are some diagrams here, but not very clear.

https://www.google.com/search?q=nissan+pathfinder+brake+booster+hose+diagram

Service Manuals

https://www.google.com/search?q=nissan+pathfinder+brake+booster+hose+diagram

..

http://forums.nicoclub.com/96-pathy-knock-sensor-location-t483742.html

http://www.autozone.com/autozone/repairguides/Nissan-Pick-ups-and-Pathfinder-1989-1995/ELECTRONIC-ENGINE-CONTROLS/Engine-Co

Borrow a repair manual for your vehicle from the libarry,

Well, let me just say that you have to remove the intake manifold (the one with 6 metal pipes) to remove the knock sensor. It is not easy to remove the intake manifold on Nissans.

this pcv valve screws into the intake manifold , theres a hose that runs from the pcv valve to the intake. heres a picture of it to help you locate it.

STARTER LOCATION ON 4.0 V6 -REMOVE ENGINE UNDER COVER.REMOVE EXHAUST MANIFOLD COVER FROM EXHAUST MANIFOLD RIGHT BANK TO GAIN ACCESS TO STARTER COVER BOLTS.THEN REMOVE STARTER COVER BOLTS AND REMOVE STARTER COVER.**** 5.6 V8 ENGINE YOU HAVE TO REMOVE INTAKE MANIFOLD TO GET TO THE STARTER.

to replace a knock sensor on a 1998 pathfinder is a big job.
you have to take out the whole intake manifold, so you can reach the sensor.
if you want to do it by yourself \, first you should have ready all the tools and parts.: including a torque wrench and a set of intake manifold gaskets. you can try here autopartsway.ca for some good cheap parts.
and be ready to work few hours if you do not have much experience as a automotive mechanic.
so, good luck, if you did not do it already.

It's located deep in the valley! Under the "LOWER intake manifold". copy and paste this link in your browser, or try clicking on it. It may be helpful to you.

http://x.nissanhelp.com/forums/pathfinder/7890-3-3l-knock-sensor-relocation.html

I didn't find this link until after I had already disassembled my truck. This is the hardest job that I've taken on thus far, hope I can put it all back together properly. I changed the gaskets on the valve covers since I had everything off.
To answer your question: It's under your lower intake manifold, so it's a hard job!

The PCV valve is located in the valve cover on the passenger side of the vehicle. The valve is closer to the firewall than it is to the front of the engine. It has a hose attached to it and threads into the valve cover.

Nissan Scope Technician- 10+ years experience is Nissan dealership