Diagnosing high pitched squeal/whistle

[HaydukeLives]

Hey guys,

My 93 2.5 is making an odd sound when up to temp. Only noticeable when off the throttle. It had an exhaust manifold bolt missing but that was replaced about 2k miles ago.

Here is a video with and without the sound.

 

[redbullet]

To find leaks I did the following with the engine off: put end of shop vacuum in tail pipe with blowing mode on, duct tape for tight seal, spray various points that can leak on manifold with soapy water, bubbles indicate a leak. Tighten anything that leaks. Have you tightened all manifold bolts to spec? Valve cover bolts? Oil fill cap tight/sealing properly?