Turned out to be the cat.
Acceleration is smooth, exhaust is a bit louder, and the occasional rattling sound has disappeared.
Oh, and the car has a new fuel filter too.
Of course the story doesn't end here...
On Thursday my daughter had an appointment to get braces. I figured I'd have time to change the fuel filter before the appointment. But the more I thought about the car's problem the more I came to believe the engine was having trouble breathing rather than getting fuel. So I went into lazy mode and took the car to a garage where they could replace the cat, if needed. They replaced the cat, fuel filter, did an oil change, tire rotation, and fixed a coolant leak (bad hoses) under the front passenger side. The leak started earlier in the week. Like I said, I went into lazy mode and had the garage do everything.
The car had never felt better when I drove it home. Took the long way and enjoyed the sound and performance.
On Saturday, I went to get gas. My car felt even better as I went into the Fiero state of mind. On the way home I watched my temp gauge get warmer and warmer. Pulled into my driveway just as I was getting concerned, got out of the car and wondered why there were drops on my driveway and green liquid coming from under the front passenger side...
Looking underneath, I saw a loose clamp hanging midway on my nice, new, lower radiator hose.
