So I replaced my bad turbo with an aftermarket one from TurboChargerPros.com, I've driven 572 miles now and the other day I noticed a loud deep sound when I'm accelerating. It starts when the turbo gauge is in the space between white and yellow. It goes away when I push the turbo into yellow, then comes back with a dissipating sound to it when the turbo spools down from yellow to white. I'm thinking it's the wastegate. Any other ideas?

Have you sorted this out yet?

What sort of sound is it? Do you have boost?

No I haven't, It sounds like someone is blowing over the top of an empty glass bottle. I'm going to be taking it in to the shop today so the mech can take a listen to it.

This kinda sounds like what it could be: http://www.oocities.org/griegerb/boschbov.html
"The second note is that the BOV makes a new sound. It hoots like an owl as you cross from vacuum to boost. If you hold it hovering around 0 PSI (mmHg), it sounds like a miniature fog horn! This is normal. Some say the new Bosch ones and the Porsche ones do not hoot, but I suspect they do. The 90 degree bend in the valve makes rushing air cross it like blowing over a coke bottle. You get a sound because of the shape, not because of the parts used in each. The Porsche one is said to whistle however, and would do so for the same reason!"

This one as well:
http://www.saabscene.com/forum/threa...top-of-bottle?

I've isolated the sound to the right front side of the engine bay. Right around the mass air flow sensor. Mini foghorn sound on acceleration. Was able to replicate the sound while stationary by putting it in drive, applying brake and accelerating to orange.

Sounds like it could be a loose hose. The dump valve is on the gearbox side of the engine (left as you sit in the car) so it shouldn't be that.

The items on the right are the airfilter and MAF then going to the COBRA anf turbo. Check that the hose from the MAF isn't rubbed through as the belts are quite close. also check all the hose connections are tight. next check the air filter lid (on the bottom) is tight.

The noise is (obviuosly) air being drawn in. If you have smoke on hard acceleration then it's more likely to be on the high pressure side due to the engine management overcompensating with fuel.

Alright! I shall check those. There's no smoke on hard acceleration, so its not on the high pressure side.

My Saab does the same thing, and I am not worried at all. It only started occurring after I put an open air intake on it. Have you fiddled with yours?