Low Vacuum, Backfire, whistle noise.

[Mr. white]

So, I have been battling with this whistle noise on my car for awhile. Whenever I apply throttle pressure, there is a whistle noise that presents itself. it gets louder the more pressure I put on the throttle. The car also back fires quite often. I thought it could be the gasket at the compressor inlet. So, i replaced that. The car responds much better (there was no gasket beforehand for some reason) now. But, the whistle is still there. It sounds like it is coming more from the intake side of the car although I can't pin point exactly and it only happens under load.

Also, my Profec b reads between -.63/-.64 which I believe is -13inhg of vacuum or so. I have checked vacuum lines visually and they seem to be fine. I replaced my TB gasket today as the old one was stuck to the Intake manifold. Idle is very lumpy, but it seems to drive fine under load disregarding the whistle at all rpms. I have also replaced the intercooler piping and couplings for better ones.

I really need some help guys, I am so stumped as to what it could be and dunno what to do next.

[jr_ss]

Have you sprayed any and all your hose connections or anywhere the motor can leak boost/vac with carb cleaner? Once you hit the spot with the motor running you'll know. I'd also check your exhaust manifold to turbo exhaust housing inlet gasket. They are known to go bad and cause all types of odd noises.

[Kingtal0n]

idle vacuum should be close to 18" unless you have serious cams

I get 15" cruising at 40mph in the city
and around 11"-12" on the highway at 70mph (3k)

make sure your profec has a good vacuum source. often profec "problems" are due to a bad source vacuum.

your issue sounds like a simple boost leak. Build a boost leak checker and pressurize the plumbing to find all the leaks. It should hold a steady pressure, even 15psi in the plumbing for 10-15 seconds or more. If it leaks out in less than 5 seconds you need to do maintenance.

[KoukiMonsta]

Boost leak..

[Mr. white]

I hope this isn't a dumb question, but could a hole like this that was unplugged cause some of my problems?:

http://www.full-race.com/store/images/full/nissan-sr20det-twinscroll-3-downpipe-content-1.jpg

[jr_ss]

Intake or exhaust? Having a hole like that on either isn't a good thing and yes, it is infact a dumb question.

[xGUNKX]

boost leak for sure