[Supras] How do I locate an exhaust leak?

[LN]

I have an exhaust leaking sound in the engine
compartment area but can't tell where it is
originating from exactly.  I took it to the local
Midas shop and they say it's the exhaust manifold
which cracked.  Afterward back at home I took the 2
heat shields off the exhaust  manifold but could not
see any cracks ( at least visible to the naked eye)
usingboth a flashlight and mirror to see the back
side.  Can someone suggest a way to locate the exact
position for a leak??  Maybe it's in the down pipe? 
How about using soap solution or will that won't work
due to the high heat ?


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