[Bill Grissom]

The dealer guys sound like idiots. I had a cracked flex-plate. The engine ran fine, it just made noises. It is easy to check for a plugged catalytic converter, using a vacuum gage on the intake manifold. This has been done for decades, long before converters (plugged mufflers). Find a decent mechanic. A plugged exhaust will cause exactly your symptoms. With air flow choked, you get no power.

I also read that sugar in the gas causing problems is a myth. Usually, what plugs converters is too much fuel makes them run hot and the ceramic melts. "Converter don't die, they are murdered" is the Car Talk guys line. If you just change the converter, the next one will quickly be murdered. Find the culprit, which is likely the degraded fuel injector harness wires. Search and you will find photos. Common, and easy to fix.