Finding exhaust leak , also update: 92 Bonneville bucking when hot

Hello there. A few months ago, I posted a message asking for help with my 92 Bonneville SE... it was losing power (alternating between accelerating and not, but only when hot, and only under heavy
acceleration.) Anyway, I did a few more diagnostic tests.... turns out the wires I had in there were burned to a crisp (white and charred.) They were only a couple thousand miles old, but they were cheap. I replaced them with a set of Bosch wires --- those worked fine for a while, but the problem returned, though it's nowhere near as severe as it was before.
But it's the same situation --- under load, after the engine is very hot, when I try to accelerate heavily, the engine misfires, or backfires, or whatever it does, just gives no acceleration except in intermittent bursts.
I've tried to see if there is a particular cylinder causing the problem by disconnecting the spark plug wires... they keep arcing to the body, the coil module, or whatever else is closest to the end of the wire.
I got a vacuum gauge and replaced all my vacuum hoses --- they were glazed and cracked. Same vacuum gauge tells me there's no exhaust restriction... and it holds steady at idle and under constant acceleration.
I can feel some air moving behind the engine block, even when the fans are off. And when I depress the accelerator mechanism, I feel more air flow by. I verified this with a piece of tissue paper. I used a mirror, however, and I can't find any holes (though there are plenty of connections rusted to hell and surrounded with rings of metal.) A few months ago, the car was giving me a lean engine code too... but that went away after a while.
On the other hand, I don't hear the "click-click-click" noise that should be characteristic of an exhaust leak --- at least not at idle. At higher RPMs I'll hear something in time with the engine, and it does get louder as the RPMS go up (at some RPM ranges, the engine noise drowns out the noise... at others, the noise is audible.) I can't verify if it's an exhaust leak without seeing the actual hole, though, can I?
How can I find exactly where the exhaust is? I've tried partially blocking the exhaust, spraying a little water in the throttle body... nothing.
thanks!
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Testing for an exhaust blockage is done like this:
Put the vacuum gauge on, have someone start the car. See if the gauge goes towards pressure, or takes a while to obtain a vacuum reading.
While the engine is running, only the blockages closest to a total blockage will show.
I believe your leak is from a restriction, leaking out at the sintered steel exhaust gasket, where the springs that mount the flange would allow or a little leak.
Refinish King

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Ah. I tested it today with a vacuum gauge and a friend... as soon as the car started, I got full vacuum. I doubt it's an exhaust leak. Also, I don't see any springs...
Thanks a lot!
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