Not sure whether it is the secondary turbo making the noise or something in my intake/exhuast system, but after I get on it in first, my boost will drop to around 5 psi at 4800 rpm and when I shift, I will have no boost whatsoever and it takes 5-6 seconds to build boost from 4000 rpm. If I let off the throttle, it makes a strange noise that I cannot describe. I have a Pettit Racing Dual Cone intake, 3" downpipe, hi-flow cat, Apex'I N1 exhaust. All vacuum lines were checked and ones that looked brittle were replaced. Wastegate is functioning correctly also. Any suggestions would be appreciated.
-r0gu3

 

does the strange noise sound like a high pitch triwling like, ok this may sound kind of childish but there is a chils toy that is essentially a short flute with a turbine in it that makes that spinning noise when u blow into it. A lot of people describe the noise i think you are hearing as the dreaded "spooling down" if something hit one of the blades on ur secondary turbo and made it go the slightest bit off balance ur not gonna get much booost outta it. ull know somethin is wrong if u stat to see the turbo leaking oil. the fan inside is lubricated with oul and if the fan is off balance it will slowly wear down the gasket and start leaking oil. that happened to mine i few weeks ago and i am told the only thing i can do is buy new/ rebuild

 

Yes I would agree. If the noise is what MazdaMike is describing that is the first sighns of tubine failure. Better start looking for a used set of twins.

 

Yes, that is exactly the sound I am hearing. But sometimes I get full boost from my secondary turbo now. It's weird ... I don't know what else it could be.
-r0gu3