I am having some wierd resonses from the stock twins. Sometimes I get no boost at all, sometimes it boosts up to 10psi everytime. sometimes it will only start boosting when I get into 3rd gear, and other times I"ll only hit 5psi then it falls while under throttle with the Bypass valve whinning like a sequential BOV.

I've inspected most all of the vaccum lines and intercooler piping, Bypass valves etc. with no luck. I've also replaced all of my check valves. This is something that has been going on now for a while. The car runs great otherwise. any ideas?

 

Couple questions about your set-up before throwing ideas out there.

stock turbos I'm guessing? Seq or non-seq? stock ECU or PFC? How are you controlling boost (stock ecu + pills, PFC, EBC, MBC)? You say you've checked most of the vac lines. Which one's haven't you checked?

 

maybe this will help.
maybe you have some off the hoses misrouted?

what upgrades do you have? i hear you atleast have a boost gauge...Right.
what boost pattern do you see? 10-8-10

 

wow. great diagram!

I am running stock twins, stock ecu, manual boost controller

 

You're running stock boost with the stock ecu, but you're using a MBC? Are you running non-seq? If you're still seq, how did disable the ecu's ability to regulate the boost pattern and how did you set up your MBC?