Actually, that might be the case too. The motor mounts are about 50k miles and a few years old, so they might be due for replacement pretty soon. I've been digging through the cd looking for the entry on motor mounts (anyone know of the number offhand? ) I also gave my exhaust system a visual inspection - there are a couple places near the exhaust manifold where clearance is tight and there might be some contact, but I tugged the parts around a bit and didn't feel any movement. I didn't see any parts damage, will have to try sealing off the tailpipe tomorrow.

Upon further investigation, I've discovered that there are multiple things making noise with my car. There's a rustling noise that varies directly with engine speed, and I think this might be traceable to the exhaust system. There's also another ticking sound that occurs when the engine is under light load - it disappears with acceleration and when I completely lift off the throttle. I haven't decided if this is the same beast that pops up on the highway. And all of the sounds seem to be coming from the front passenger footwell.

The mystery deepens...

thanks,
anthony

p.s. As a sidenote, it's amazing how quiet these cars are with the radio and hvac off. I think below 40 mph, the fan blower is louder than the wind, road, and engine noise combined..