I have had a "fluttering" sound from the engine for a while now, when accelerating (with boost) from low rpms, especially in 3rd and OD. Only happens under boost. It definitely changes with the rpms, and is more noticeable after I installed the single blade throttle body. The sound goes away after the rpms get up around 3000, which it seems like everyone on here who has a "fluttering" sound is getting it to START happening at around 3000 rpm?? Runs great at WOT, no flutter. I dont have a chip, just an Airaid filter and the single blade T/B.
Does this sound like detonation or could it just be the boost wastegate?

 

Start with this thread for info.:

https://www.f150online.com/f150board...ML/003180.html

Then try doing a search for "flutter" It will tell you everything you never wanted to know about it.

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There is also some kind of warranty replacement of BOTH belts that have resolved a similar problem for a few on this board...

I have the same thing, and my belts are supposed to be replaced next week.

I'll let you know if this solves "my" problem...