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.

[4cefed]

This sounds to be most likely the intake manifold gasket, probably the only one you haven't changed yet.

[IanS]

This sounds to be most likely the intake manifold gasket, probably the only one you haven't changed yet.

I must agree. Build a boost leak tester out of a PVC plug and a bicycle tire valve stem. Search and you will find a great write up on how to build/use one.

[PapaSmurf2k3]

Or buy something flammable (starting fluid/propane) and spray around suspect areas while the vehicle is running and listen for it to idle up.

[Mr. White]

I've done a Boost leak test, but I thought that air was not supposed to pas the throttle body when testing?

I took the IM off again today and re-seated it just incase I didn't put it on right the first time. The gasket is metal, which I thought you could reuse?

I've been sprayin Starter fluid around the engine for the past week. Only the Intake side, though.

I also tightened my BOV down some more. when I started the car my Vacuum went up to another inch of hg or so. But, my idle was lower. During warm up, it stays around 600-700 and when it is warmed up, It only idles at about 850-900 now, when before it was at about 1000 but I had less vacuum. Also, now my PFC reads my timing at 20deg as opposed to 15 before.