Boost surge maybe?

The fluttering is from your bov. This can happen when you boost pre tb is higher then the the boost post tb.
Research Compressor surge. Its not good for the car.

Do a boost leak test and check your turbo for shaft play. Metal expands and contracts when hot/cold. Your motor may be rebuilt but everything bolted to it needs to be checked out too.

It sounds like compressor surge, but does not explain why it goes away after being warmed up. . .

I will do the boost leak test and check for shaft play. The part that confuses me is as soon as the car is up to normal running temperature the sound goes away.

Ok so I tinkered with the car some. There is shaft play side to side id say an 1/8 of a inch. Zero shaft play In and out. I took the car for a drive It continued to make the fluttering sound. Soon as the temperature gauge read normal the noise stopped. Is it possible The oil or coolant eliminates the shaft play?

Also is that amount of shaft play acceptable? I have a evo 3 16g I will be swapping later on. Or is the shaft play something I need to address right away?

Shaft expands= less play

As a general rule, you should not be boosting the car before it is fully warmed up. Given that there are several alloys in our engines that all have different thermal expansion rates, you have to give the engine time to warm up so the components in the rotating assembly can expand to ensure proper clearance and prevent engine damage. Stock pistons, for instance, expand less than after market forged units and are less prone to piston slap because they can have a tighter PTW (piston to wall clearance). Even so, a bone stock motor should be brought to full operating temperature before being put under heavy load (boosting). Just like a turbo timer allows the turbo to cool and prevent oil coking on the CHRA and turbine shaft, which adds to the longevity of your turbo... Properly warming up your engine before putting it under load will make it last longer and make it less prone to premature wear/failure.

Now to address your original question, it sounds like compressor surge, but without hearing it, diagnosis is difficult. Not that I recommend boosting while the engine is sub operating temp, but do you hear your BOV operating when you hear this fluttering sound? I have several ideas as to what could be causing the problem but I don't want to send you in the wrong direction. Please make a video of the problem and post a link here. You can also PM me and we could attempt diagnosis over the phone. Feel free to contact me for further assistance. Good luck, and happy boosting.

PS... Keep this in mind... Would you dive in balls deep the instant you got a girls panties off... Or take the time to warm her up first and get her hot and ready to ride? Treat your car like you would a hot girl you're getting ready to do the deed with and she will always make you happy in return. Just my 2 cents. Hope I haven't scarred the poor children. Now I kinda feel like Chef.

4g63and420a said:

There is shaft play side to side id say an 1/8 of a inch.

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That's bad news. You should definitely get that rebuilt before it causes wheel damage and turns the entire turbo into a boat anchor if it hasn't already.

What weight oil is in it? How does your oil pressure look?

Could be an exhaust leak pre Turbo.

Well I ignored the sound and now I believe im paying for it. Today I took the car out for a drive and out of now where I have no boost, my turbo sounds like a jet turbine an white thick smoke is pouring out of my exhaust pipe. Took it easy going back home. Checked a few things out all looks good. It idles fine an no smoke. Rode up and down the street a few times and its only emitting white smoke when the turbo spools up. I have bad side to side shaft play and some in and out play on the stock turbo.

Sounds like I blew a seal in the turbo. Just looking for a second opinion.

4g63and420a said:

Sounds like I blew a seal in the turbo. Just looking for a second opinion.

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Ummm....

4g63and420a said:

I have bad side to side shaft play and some in and out play on the stock turbo.

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You have a lot more going on there than a leaky seal. Time to start turbo shopping.

More frightening is how quickly that in/out play came on. That's almost definitely a sign of oil contamination blocking the oiling hole to the thrust plate.

Might be your bov? thats all i can think of

When I first read it I was thinking it was the manifold to turbo gasket. Either blown or the bolts arent torqued down. I guess you already figured it out though

My car did the same thing with the fluttering sound, except it did it either cold or hot, and I do have a HKS ssq bov which also makes a fluttering sound at low boost while driving. If I rev the car via the throttle body when its parked it makes the fluttering sound as well, but sounds like its coming out of the maf. I figured this was the bov, and now I'm worried about it too.