I have a trustworthy dealer here in western New York state. Today I had the service manager offer an opinion on the source of a new throaty sound in the engine compartment. His verdict: possibly an insulted gasket from the recent tear-down for replacng the internal timing belt (at a different dealer's shop), but more likely the front exhaust pipe failing after 85K miles and eight salty winters.
He quoted the cost of the latter replacement as $1200 - $1500 because the front exhaust pipe includes a catalytic converter, separate from the CC farther along in the exhaust-parts sequence.
The rest of the the exhaust system is original and solid.
Does anything about this narrative strike you as out of the ordinary for a babied, rigorously serviced '98 Avalon?