What happens to vac controlled items under boost?
 

Things like cruise control, power brakes etc. Do we have to put in a one way valve so it does not damage these items? Thanks for the replys

you'll never brake in boost, unless you have really weird driving habits.

Dunno about cruise.

Edit: You *will* want to address your PCV system though.

What do you mean?

Well, if you routed your PCV breather hoses incorrectly on a car with forced-induction, you could introduce a bunch of pressure into the crankcase, break-down rings, blow seals, etc.

the brake booster line has a check valve from the factory.

throw in a one way check vavle on the cruise and charcol cansiter. i believe the msm has a few others on select lines.

The check valve will work for the brake, cruise and charcol cannister for sure and yeh braking under boost would not be likely. I would anticipate that the cruise will drop off if you were cruising and started up a hill because boost would eventually exceed the vac and cruise lets go... correct?

The whole PCV system is what got me thinking about it. I have read several threads and there seems to be a couple of opinions on how to do it. There is a PCV check valve coming off the valve cover to the intake manifold which under boost should close, so that seems straight forward. The other line coming out of the valve cover on OEM goes into the intake just before the Throttle Body however that would not work with FI as you do not want boost in the crankcase so what is the "final" wisdom on what to do with this line? Some people have said to vent it to atmosphere with a little filter, others said to run it to the intake side of the turbo around the air filter and there seems to be another version although I cannot remember what it is????

Another option would be route PCV to catch can (to accumulate oil) then to intake side of turbo (after mafs)

OR - PCV to catch can to atmosphere.

You can make a catch can out of just about anything

or valve cover straight to intake, the end.

That's what I did. :)

I left my PCV valve alone and ran a hose off the other side of my valve cover to a catch can with a mini air filter on it

When I turbo'd my non-turbo ka24de 240sx I had no problems with cruise control and I made no changes to the system. Didn't add a check valve or anything and the car would go into boost when on cruise control if I was going up a hill.

Maybe the nissan system is different than Mazda's but I had zero problems leaving it alone.