FJ60 Whistle at 2500rpm

[MJM]

I now hear this whistle at 2500 rpm and above it is load enough to turn heads and I can hear it in the cab. Any thoughts on what to check first.
Fully smogged 83FJ60 40k on a rebuilt 2F

 

[sterling]

I have a low rpm whistle that comes and goes
Possible culprits are leaky exhaust manifold gasket or the gasket under the carb.
Have you replaced any vacuum lines?
Maybe some are old and dry rotted, causing the whislte
Still tracking mine down
good luck

 

[Texx]

Whistle is almost always a vacuum leak. Check around the carb base area.