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Originally Posted by Danger_Dorn
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I believe the -8 psi you mean 8 inhg, or 8 on the vacuum side of your boost gauge (needle indicator read, analog/manual gauge. Above zero (aka boost) is read in psi, below zero (aka vacuum) is read in inhg). These gauges already make the calculation for you. If the needle points to 5 ABOVE zero your boosting 5 psi. If your idling or cruising along and your needle points to 5 BELOW zero then you are reading 5 inhg. If this is correct and you really are at 8 inhg you have a leak somewhere.
If you have a digital boost gauge that shows readings ONLY in psi (digital l.e.d. display with 2 or 3 digit capability) then your fine (-8 psi (in the sense that it ONLY displays readings in PSI ) is 16 inhg) @ idle/vacuum then you dont have a leak more than likely. (Keep in mind there are digital boost gauges that are programmed to read like the first gauge i described above. It always helps to know what type of gauge your using and how exaclty it performs)
Have you done a compression test of all 4 cylinders? Shouldn't be bad after a rebuild but you never know.
If your pcv is in the valve cover but has some play when moving it around or you can pull it out of the valve cover with literally no force try this:
Pull the pcv T off the valve cover. Clean the exposed port on the T, and the opening where it is inserted in the valve cover.. Take a small layer of electrical tape and wrap the exposed T port once, maybe twice at the max. Dont block the pcv lines or port opening in anyway. Your car has to have a pcv system. Now with a bit of force push the pcv valve port (wrapped in tape) back into the valve cover. Its ok if the tape sort of slides back a little but you should notice a stiffer difference than when you first pulled it out. It should slide back in with small force and the tape acts as a seal between the port going into the valve cover, and the actual valve cover opening itself. If thats what fixes your vacuum leak then you know and will now have to seal it the right way asap (that tape won't last long). A rubber sleeve or a bit of shrink wrap over the end would probably hold longer. Thats what I ended up doing to fix my vacuum leak. Better seal means better vacuum. Hope that helps.
Also just double checking. You said your catch can setup includes an atmospheric vent? :
Oil drain back into engine block ---- pcv T ----- catch can ----- intake boot nipple ()
#########################Valve cover##########################
THIS IS MY CATCH CAN WITH PCV ROUTING. ITS WORKED FOR ME FLAWLESSLY
If I remember correctly on turbocharged vehicles you CANNOT vent pcv to atmosphere like you can on a Naturally Aspirated engine.
NOT TRYING TO FLOOD YOU WITH INFORMATION, BUT HERE IS A WAY TO HUNT FOR VACUUM LEAKS :
you can develop vacuum leaks from small things really. A can of ether is your best friend in a way. Go along spraying it where a vacuum leak could occur (intake manifold gasket, throttle body, bov, intercooler, intercooler piping, all your clamps, etc) Only if nothing else seems to of worked and the compression test passed. If you have a vacuum leak whenever you spray that ether on the vacuum leak you should get a noticeable change in idle. E.G: engine is idleing, normal temps, you spray the intake manifold where it meets the cylinder head by intake runner number 2 with a mist of ether, you notice your idle kicks up for a couple seconds then goes back. If this spot affects your idle from the ether being sucked into the system you have found your vacuum leak, which in this hypothetical case could be a loose manifold or bad intake gasket. This is an all out if everything has failed. Ether is extremely flamible and dousing your engine in it isn't a bright idea but in easy moderation it can help you find your leak.
If you didn't know ether is basicly starting fluid. Also don't spray in a way that will suck ether thru your maf. They tend to not like it