Whistle on Overun

Ive just notices a Weird Whistling Noise when slowing down using gears.
Im guessing its air leaking or been sucked in to the engine. Nothing to see in engine compartment and can not reproduce noise when stationary.
The sound is reminiscent of whistling rocket fireworks.

Before I start taking bits off the engine I would like your thoughts on this
1 ltr no mods

Thanks
 
Back
Top