Ahhh...Superman's Obsession (ie:exhaust popping) rises, yet again, to the fore.
Hey Jim...Unless your car sounds like the 4th of July,
it's normal! Especially if your cat is gutted or removed. The Decel valve also has an effect on this as well.
This "normal" bit of popping is caused by a momentary lean mixture as the throttle is lifted, along with a simultaneous high manifold vacuum.
And if you want to listen for *real* exhaust leaks, do as your wrench suggested, but use a
wet rag, rather than your bare hand, over the tail-pipe.
(So when
are we dropping that motor?)
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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website
"If it ain't broke...we'll help you fix it 'til it is!"