So in addition to the other things that my LS has picked up with the addition of the Skunk2 IM, there's now a fairly discernable noise whenever you're at low/mid rpms and trying to accelerate. its definitely something new. I noticed it when I picked my car up from the shop that did the install. Its kind of a whirring/humming/trilling kind of noise. I'd say you hear it between 1k and 3500 rpms. though I've heard it when I'm starting from a stop if I give it WOT. is it just that the intake manifold is sucking in more air and that's making my filter whistle or is there something else going on here? I still have the stock LS TB and I kind of wonder if that might be it. Unfortunately I haven't been able to replicate the noise when I'm in the engine bay, pulling on the throttle cable so I can't pinpoint where its coming from.

 

vacuum leak? thats all i can think of.

my car has developed a whirring noise too, but its there at idle... goes away sometimes, comes back sometimes... obviously not the same problem.

anyways, did you use a new gasket when installing the intake manifold? the shop will tend to just reuse the old cruddy one if it looks ok... the reason why the filter would whistle is cuz of a vacuum leak also. so if its the same kinda noise, you got a leak somewhere.