My 93 SE (no modifications at all) has developed an annoying "throaty" exhaust leak under moderate load. If I'm accelerating from a dead stop and the go more than 1/3 throttle I can hear the exhaust leak from in the engine compartment. And likewise, merging on the expressway I'll get the same exhaust noise with more than 1/2 throttle. The noise really reminds me of an old V8 engine with worn out exhaust donuts.

The car runs great and doesn't seem to have any effect on performance, but I'm just curious what would be causing the noise? A leaking tailpipe or manifold should make it noisy all the time. The leaky manifold would probably cause performance issues too. But, I'm seeing none of that.

Tonight I'm going to change the oxygen sensor as preventative maintenance (156,000 miles and still the original!!!) so I'm searching for things to look at regarding the noisy exhaust while I'm under there.

While you're changing the O2 sensor, check the packing in the transition from the rear manifold to the downpipe. Also make sure the bolts/springs are tight.